Atomic-layer deposition apparatus

ABSTRACT

A thin film deposition system for depositing a thin film on a moveable substrate using atmospheric pressure atomic-layer deposition includes a chamber and a moveable substrate having a levitation stabilizing structure located on the moveable substrate that defines an enclosed interior impingement area of the moveable substrate. A stationary support, located in the chamber, supports the moveable substrate. The stationary support extends beyond the enclosed interior impingement area. A pressurized-fluid source provides a fluid flow through the stationary support that impinges on the moveable substrate within the enclosed interior impingement area of the moveable substrate sufficient to levitate the moveable substrate and expose the moveable substrate to the fluid while restricting the lateral motion of the moveable substrate with the levitation stabilizing structure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of prior U.S. patent application Ser.No. 14/621,423, filed Feb. 13, 2015, which is hereby incorporated hereinby reference in its entirety].

FIELD OF THE INVENTION

The present invention relates to methods, equipment, and structures fordepositing atomic layers on a substrate by employing Bernoulli effects.

BACKGROUND OF THE INVENTION

In general, the processing of substrates refers to the various stepsperformed or carried out to modify either the surface of a substratematerial layer, the material layer of substrate itself, or both thesurface of the material layer of the substrate and the material layer ofthe substrate itself in order to modify and change the functionality ofthe substrate for a specific purpose. The change in functionality of thesubstrate is often the result of a modification or change in either theactual properties of the material layer of the substrate itself or achange in the actual properties of surface of the material layer of thesubstrate. The steps performed during substrate processing may bestraightforward. For example, a substrate may be heated to eitherrelieve stress by thermal relaxation or to change the physical hardnessof the substrate. In both cases changes in the physical properties ofthe entire substrate material layer and surface take place. In anotherexample of substrate processing, the surface of the substrate materiallayer may be cleaned using any means known in the art, such as, forexample exposure of the substrate material layer to a combination ofultraviolet light and ozone gas, in order to achieve a demonstrablechange in an easily measured metric like contact angle when wetted by adrop of a fluid of known surface tension. The processing of thesubstrate material layer by means of exposure to ultraviolet light andozone gas is employed to modify the wetting properties of the surfacesubstrate thereby affecting a change in the surface energy of thesurface of the substrate material layer. Processing of substrates may bemore complicated, involving steps associated with changing thefunctionality of the material layer substantially by modifying thechemical composition of the surface of the substrate material layer orthe material layer of the substrate itself. In particular, theprocessing of substrates may result in changes in functionality of thesubstrate or substrate surface that include alteration of the physicalproperties of the near surface region of the substrate to achievedesirable physical properties such as increased conductivity orincreased resistivity, specific optical properties, specific surfaceenergy, specific chemical reactivity, improved surface topography, andthe like. Substrate processing to modify the surface of a substrate iswell known in the art of fabrication of integrated circuits where theprocessing steps and sequences of processing steps have specificpurposes. For example, deposition processing, often referred to just as“deposition”, may be used to alter the surface composition of asubstrate by adding a material layer to a substrate surface by means ofa wide variety of methods known in the art for adding a material layerto a surface. Methods for adding a material layer to a substrate orsupport are well known to those familiar with the art of deposition, canbe highly specialized, encompassing a vast array of technologies, andcan include such methods as, for example, physical vapor deposition byevaporation and sputtering, chemical vapor deposition, plasma enhancedchemical vapor deposition, electrostatic mist deposition,electrochemical deposition (plating), electroless deposition, spincoating, hopper coating, gravure coating, flexographic printing, silkscreen printing, deposition by brush application or spray,electro-spray, thermal plasma, and the like.

Deposition processing is known as an additive processing method becausea material layer is added to the surface of the substrate material layeror substrate surface, resulting in a film of measurable thickness placedover and in contact with the substrate surface. Similarly, there issubtractive processing accomplished by means of subtractive processes,that is used to change the functionality of substrate surface byremoving a measurable quantity of a material from the substrate surface.Examples of subtractive processes familiar to those knowledgeable in theart of subtractive processing include plasma etching and plasmastripping processes and chemistries, non-plasma based etching andstripping processes employing both the condensed and vapor phase etchantand/or stripping chemistries, electrochemical stripping processes,abrasive polishing processes, cleaning processes, sand blasting, gritblasting, and the like.

The terminology employed in the art for the material layer that issubjected to processes or undergoes processing is highly varied. In thisdocument the material layer that is exposed to and removed from variousprocessing steps and processes is called the substrate. Elsewhere in theart the material layer that undergoes processing is called the support,the workpiece, a slice, a wafer, an object, a web, and is alsoidentified by numerous other terms. The context and description found inthe art where the term describing the material layer undergoingprocessing occurs makes clear when the term “substrate” as employed herecan be used interchangeably with the term employed in the art that isused to describe the material layer that is subjected to processes orundergoes processing.

Fluidic Levitation

The substrate processing quality is determined at least in part by thedefect levels on the substrate after processing. There are many factorsthat can prevent acceptable substrate processing by introducingsubstrate defects. Two factors contributing to substrate defect levelsafter processing are particle contamination and substrate physicalcontact. Both particle contamination of the substrate surface andphysical contact with either the substrate material layer or thesubstrate surface can lead to unacceptable substrate defects, some ofwhich are manifest as defects in the uniformity of the surfaceproperties of the substrate after processing. The measurement of thenumber of defects by any known method such as, for example, lightscattering from the surface of the substrate, is known as defectivity.In substrate processing applications where it is important to controldefectivity, effort has been made to develop methods that minimizeparticle contamination and physical contact with the substrate surface.Examples of processes where it is important to control defectivity areoptical film deposition, deposition of encapsulation films, andintegrated circuit manufacture. In these examples, the substrate may beplanar and plate-like, non-planar with complex surface features,spherical, or spheroidal. An example of a planar or plate-like substratewould be a silicon wafer or a glass plate upon which integrated circuitelements are fabricated. An example of a non-planar substrate with acomplex shape would be a lens upon which an antireflection film isdeposited. A substrate may also be flexible, for example, like a web ofpolymer film, a flexible web of glass, a long ribbon of metal, or alarge sheet of glass. An example of a substrate that is flexible andnon-planar is a spool of wire that is to be cleaned prior to applicationof an electrically insulating coating using additive processing. Thedesire to minimize particle contamination of the substrate surface andeliminate physical contact with the sample during processing has led tothe development of specialized substrate handling methods based onfluidic levitation.

In general, flows of gases over a surface are known and in particularBernoulli effects are known. Levitation refers to the process ofsuspending an object in a medium without the use of physical supportscontacting the object. In the scientific literature, levitation is theprocess by which an object is suspended by a physical force, against theforce of gravity, in a stable position without the use of physicalcontact. Fluidic levitation refers to the process of levitation wherethe physical force suspending the object in a stable position againstthe force of gravity is produced by means of a fluid said fluid being amoving fluid or a stationary fluid. Fluidic levitation can employdifferent types of fluids, said fluid being either gaseous compressiblefluids or condensed non-compressible liquids. The term compressiblerefers to a fluid whose density is strongly pressure dependent.

For the purposes of the invention the term “moveable substrate” refersto a substrate that undergoes positional displacement during fluidiclevitation upon exposure to a fluidic flow employed for the purpose ofinducing fluidic levitation of the substrate and opposing the force ofgravity during said levitation state. The term “stationary support”refers to a stationary fluid emitting element that is employed for thepurpose of supplying a fluidic flow, said fluidic flow being employedfor the purpose of inducing fluidic levitation of the moveable substrateand producing fluidic forces opposing the force of gravity when themoveable substrate is in a levitated state. The term “support duringlevitation” means that the moveable substrate can be levitated by fluidflow emanating from the stationary support so that gravitational forceon the moveable substrate is opposed by the force of a fluidic flow. Incontrast to moveable substrates, conventional substrates are fixed inposition during processing, for example, using mechanical restraints,vacuum chucks, or electrostatic chucks.

Fluidic levitation is useful for manipulating a substrate duringprocessing and, as a method for sample manipulation, may encompass andadvantageously enable many different varieties of substrate processing.There are many substrate processes that require exposure of thesubstrate surface to chemically reactive substances for the purpose ofmodifying or changing the properties of the substrate. The prior artdisclosing substrate processing with fluidic levitation methods makeslittle mention of any issues associated with incorporating chemicallyreactive materials into the levitating fluid flow for the purpose ofsubstrate processing. This is surprising because the problems associatedwith the handling, manipulation, and fluid transport of chemicallyreactive materials is well known. Some of these problems are 1)corrosion and dissolution of the materials of construction employed forthe pumps, gauges, valves, tubing, and connections in the fluid deliverysystem leading to equipment failure and 2) deposit build-up at variouslocations in the fluid system from unintended side reactions of reactivespecies in the fluid with the materials of construction of the fluiddelivery system which can lead to changes in the fluid flow and fluidpressure during fluid delivery system operation. Furthermore, thephysical positions of substrates that are subject to fluidic levitationtend to be unstable and the substrate position is mechanicallycontrolled. This mechanical control can induce particulate contaminationor damage to the substrate.

U.S. Pat. No. 3,627,590 describes a method for processing a workpiece,for example, a slice of semiconductor material or a wafer of asemiconductor, by floating the substrate on a layer of gas during theseries of processing steps required for thin-film processing. Twoprocesses are disclosed in U.S. Pat. No. 3,627,590: heat treatment forenhanced diffusion of a dopant into a film and film deposition by meansof thermal decomposition of a thermally unstable precursor. The layer ofgas prevents physical contact with the workpiece during processing. Theworkpiece described in U.S. Pat. No. 3,627,590 is a substrate. U.S. Pat.No. 3,627,590 teaches that film deposition with thermally unstableprecursors can be managed when the decomposition temperature of theprecursor is high and the thermally decomposable precursor can be keptaway from and isolated from portions of the equipment that operate atelevated temperature. However, U.S. Pat. No. 3,627,590 does not teach ordisclose a method or apparatus to control and manage the reactivity ofthe fluid flow as it comes in contact with different surfaces of thefluid delivery system and associated equipment.

The apparatus described in U.S. Pat. No. 3,627,590 is called apressurized fluid pickup device and is described further by Mammel inU.S. Pat. No. 3,466,079. In U.S. Pat. No. 3,466,079 the term “slice” isused to describe the substrate. According to U.S. Pat. No. 3,466,079 itis “ . . . nearly impossible to center the exit orifice for thepressurized fluid over the support . . . . As a result, there is a forcecomponent tending to laterally shift the slice relative to the referencesurface”. This is another way of saying that, left to itself, theslice—which is the substrate—will shift and move laterally in a sidewisemanner until none of the surface area of the slice is exposed to thepressurized fluid flow. Lateral motion means that the substrate moveshorizontally in a sidewise manner that is parallel to the stationarysupport and the plane of the layer of gas upon which the substrate isfloating. In other words, the lateral motion of the substrate slicemoves the substrate away from the pressurized fluid emitting from thereference surface resulting in a failure of the sample to float on thegas layer. The problem identified by Mammel in U.S. Pat. No. 3,466,079is one of uncontrollable lateral motion of the substrate during fluidiclevitation because of the difficulty associated with positioning thesubstrate in the proper position over the pressurized fluid region. Thisproblem is addressed in U.S. Pat. No. 3,466,079 by the use of physicalcontact with the substrate: “Shifting of the slice is limited by thelugs 25 with either the points 26 or the rounded ends 26”. In both U.S.Pat. Nos. 3,627,590 and 3,466,079 the substrate is kept in place overthe pressurized fluid flow by the use of stops or lugs to prevent thesample from shifting position during processing.

The scientific literature describes a method for substrate handlingduring processing known as “vapor levitation” in which the substratefloats on a cushion of gas emanating from a porous surface opposed toone of the substrate surfaces. This method of substrate handling differsfrom that described in U.S. Pat. No. 3,627,590 but possesses acommonality in the difficulty of maintaining the sample position duringprocessing due to the frictionless nature of the gaseous floatationlayer which enables non-contact processing. The method is described byH. M. Cox, S. G. Hummel and V. G. Keramidas in the followingpublications: 1) “Vapor Levitation Epitaxial Growth of InGaAsP AlloysUsing Trichloride Sources” Inst. Phys. Conf. Ser. No. 79: Chapter 13,page 735 (1986); 2) “Vapor Levitation Epitaxy: System Design andPerformance”, J. Crystal Growth 79 (1986) 900-908; 3) “Vapor LevitationEpitaxy Reactor Hydrodynamics” by J. S. Osinski, S. G. Hummel and H. M.Cox, Journal of Electronic Materials 16(6) (1987) 397-403. The fluiddelivery system employed for vapor levitation epitaxy is described indetail by Cox, Hummel, and Keramidas in the article “Vapor LevitationEpitaxy: System Design and Performance” (J. Crystal Growth 79 (1986)900-908). Deposition processes that can occur in the fluid-deliverysystem are managed by operating the entire fluid-delivery system atelevated temperature and continually scrubbing by contacting thesurfaces of the fluid delivery system with reactive gases to clean thesurfaces of the fluid delivery system. The fluid-delivery systememployed for fluidic levitation of a substrate and substrate processingdisclosed in this art does not teach or disclose a method or apparatusto control and manage the reactivity of the fluid flow as it comes incontact with different surfaces of the fluid delivery system andassociated equipment.

U.S. Publication No. 2008/0122151 by Ito, Niwa, and Saito titled“Levitation Unit with Tilting Function and a Levitation Device”describes a device comprised of a frictionless spherical joint enablingfrictionless tilting of a porous gas emitting surface which is employedfor vapor levitation to support large planar objects. The mechanicalinstability of the device described in U.S. Publication No.20080122151A1 makes it difficult to see how the device can achievefluidic levitation of a substrate body on the porous gas emanatingsurface and keep the substrate body in a stable position with little orno lateral movement.

U.S. Pat. No. 6,805,749 B2 by Granneman et al. titled “Method andApparatus for Supporting a Semiconductor Wafer During Processing”describes a method for contactless processing or treatment of asubstrate such as a semiconductor wafer comprising enclosing the waferin an apparatus and applying two gas streams in opposing directions fromfirst and second side sections located opposite one another to the twoopposing planar sides or surfaces of the wafers. Although the use ofmultiple gas streams or jets is mentioned as a means of providing thelevitating fluidic flow, the preferred method of production of the gasstreams is through the use of porous plates wherein the porous platesprovide the gas passages to produce the gas streams that are used forvapor levitation according to the method described by Osinski, Hummeland Cox in Journal of Electronic Materials 16(6) (1987) 397-403. Thereis no teaching regarding elimination of lateral movement of thesubstrate in U.S. Pat. No. 6,805,749 B2 and the method described suffersthe same shortcomings common to all vapor levitation technology. U.S.Pat. No. 6,805,749 B2 mentions that the problem of “supplying processgas at elevated temperature and more particularly when depositing layersis that the apparatus used to supply the process gas becomescontaminated by deposition of the material concerned from the processgas. This means that apparatuses of this type have to be cleanedregularly and that major problems arise with regard to clogging.” [Col3, lines 9-17] This problem is managed in U.S. Pat. No. 6,805,749 B2 byoperating the apparatus in a temperature region where minimal depositioncan occur whilst not eliminating the problem. The fluid delivery systememployed for fluidic levitation of a substrate and substrate processingdisclosed in this art discloses the use of temperature control as amethod to control and manage the reactivity of the fluid flow as itcomes in contact with different surfaces of the fluid delivery systemand associated equipment.

U.S. Pat. No. 6,805,749 B2 further teaches the use of the “Bernoulliprincipal” for substrate handling suggesting that the “the Bernoulliprinciple can be used by allowing the correct gas stream to flow againstthe top of the wafer. With this arrangement a reduced pressure iscreated beneath the wafer which reduced pressure ensures that the waferwill float (in a stable manner) beneath the top side section.” U.S. Pat.No. 6,805,749 B2, contrary to all other prior art including the art ofU.S. Pat. No. 3,466,079, claims that the substrate will “float (in astable manner) beneath the top side section” in this arrangement. U.S.Pat. No. 6,805,749 B2 does not describe “the correct gas stream” and thespecification of the document is insufficient to determine exactly whatapparatus was employed to achieve the reported result. It is thoroughlyclear that U.S. Pat. No. 6,805,749 B2 does not contain a description ofany addition modification of the apparatus or disclose a specializedmethod that would enable vapor levitation with the sort of positionalstability therein described, and thus teaches against the art disclosedby Mammel in U.S. Pat. No. 3,466,079 and others. U.S. Pat. No. 6,805,749B2 also describes a method of achieving substrate rotation by alteringgas emanating channels 10. Substrate rotation can be achieved by“positioning one or more of the channels 10 at an angle with respect tothe vertical, as a result of which a spiral gas flow is generated.” Nofurther detail concerning substrate rotation is disclosed and it isunclear exactly how this rotation is implemented in the disclosedapparatus or whether stable rotation can be achieved using the disclosedapparatus.

U.S. Pat. No. 5,155,062 by Thomas G. Coleman entitled “Method forSilicon Carbide Chemical Vapor Deposition Using Levitated Wafer System”describes a method of chemical vapor deposition of silicon carbide on asubstrate where the substrate is suspended in an upward flow of gas andheated using either induction heating or microwave heating to addresscontrol of the extremely high temperatures required to prepare thedesired polytype of SiC on the substrate. The method of fluidiclevitation is not well described and appears to be similar to thatdescribed in U.S. Pat. No. 3,627,590. No teaching on the preferredmethod of fluidic levitation is given in U.S. Pat. No. 5,155,062 andthere is no detail on how reactive fluids are handled in the apparatus.U.S. Pat. No. 5,155,062 teaches the use of highly localized heatingmethods such as inductive heating of the substrate or microwave heatingof the substrate to ensure that thermal decomposition of the precursoroccurs only where elevated temperatures are present. The apparatus andmethod in this art discloses only the use of temperature control as amethod to control and manage the reactivity of the fluid flow as itcomes in contact with different surfaces of the fluid delivery systemand associated equipment. Although not shown in the drawings, U.S. Pat.No. 5,155,062 explicitly calls out a “means for aligning the substrate .. . in the form of the supporting shoulders 12a” (FIG. 1). In FIG. 2 ofU.S. Pat. No. 5,155,062 the suspended substrate that is fluidicallylevitated is located within a cavity that restrains the lateral movementof the substrate during fluidic levitation. FIGS. 1 and 2 in U.S. Pat.No. 5,155,062 indicate that Coleman recognized the difficulty inmaintain the substrate in a suitable position during processing andresorted, as in the previous art, to the use of a physical restraint, inthis case a “shoulder” on the substrate support or a cavity around thesubstrate in order to maintain the substrate in a stable position.

U.S. Pat. No. 5,370,709 by Norio Kobayashi titled “Semiconductor WaferProcessing Apparatus Having a Bernoulli Chuck” describes a method andapparatus for non-contact processing of a substrate using a pressurizedgas flow method similar to that previously disclosed in U.S. Pat. No.3,627,590. On a central portion of a suction plate in a reactionchamber, there is formed a blowing port for blowing gas to a rearsurface of the suction plate. In the blowing port, there are providedpipes for introducing carrier gas and reactant gas. Gas, which isintroduced by these pipes, and the suction plate are heated by a lampformed in the outside of the reaction chamber. If gas introduced bythese pipes and reactant gas are blown from the blowing port to the rearof the suction plate in a state that a semiconductor substrate is closeto the portion in the vicinity of the suction plate, the semiconductorsubstrate is sucked to the suction plate in a noncontact state and anepitaxial layer is formed on the semiconductor substrate in this state.

The particular process disclosed in U.S. Pat. No. 5,370,709 involves thefilm formation on a pneumatically levitated substrate by means ofthermal decomposition of a thermally decomposable volatile precursor.The apparatus disclosed uses a single orifice for delivery of the fluidflow containing the thermally decomposable reactive precursor. Thethermally unstable gas phase reactant is injected into a preheatedcarrier gas near the fluid deliver orifice and col. 5, lines 39-41 reads“The reason why reactant gas is mixed with the preheated gas is toprevent the chemical reaction of reactant gas due to heat.” It isapparent that Kobayashi recognized the issues involved in fluid deliveryof reactant species during fluidic levitation.

Although the apparatus and method in U.S. Pat. No. 5,370,709 attempts tocontrol the reactivity of the fluid flow by controlling the temperatureof the fluid flow it is difficult to see how unintended deposition ofthe reactive precursor would not occur in the orifice itself during thesemiconductor wafer processing operation since the orifice region isheated, also. With continued deposition in the heated vapor deliveryorifice during equipment operation, the orifice will eventually block,resulting in equipment failure as the diameter of the orifice decreaseswith increasing deposition. Thus, U.S. Pat. No. 5,370,709 teaches theuse of temperature control as a method to control and manage thereactivity of the fluid flow as it comes in contact with differentsurfaces of the fluid delivery system and associated equipment duringfluidic levitation.

The initial “parallel plate” configuration disclosed in FIG. 1 of U.S.Pat. No. 5,370,709 has no physical restraints for lateral movement ofthe substrate during levitation and by virtue of its similarity with theapparatus described in U.S. Pat. No. 3,466,079 would suffer from thesame problem of positional stability and lateral movement of thesubstrate during operation thereby resulting in a useless apparatus. Allsubsequent configurations disclosed in U.S. Pat. No. 5,370,709 employthe use of “stoppers” around the periphery of the substrate while it isfloating on the fluid layer of gas to prevent lateral motion of thesubstrate and keep the substrate from sliding out of position on thenearly frictionless gaseous support layer. For example the descriptionof FIG. 2 of U.S. Pat. No. 5,370,709 reads “The rear surface portion ofthe suction plate 26 is formed to be smooth and a stopper 31 is providedat four places in the periphery of the rear surface portion.” Only twoof these stoppers 31 are shown. The suction plate 26, the stopper 31,the pipes, 27, 28, 30 and the nozzle 29, are made of quartzrespectively. Thus, U.S. Pat. No. 5,370,709 teaches the necessity ofphysical stops formed on the suction plate 26 to prevent lateral motionof the substrate during fluidic levitation.

The pneumatic levitation of spherical objects in a gaseous fluid flowsis known. U.S. Pat. No. 4,302,311 entitled “Sputter Coating ofMicrospherical Substrates by Levitation” discloses pneumatic levitationof microspheres under reduced pressure conditions. The moveablesubstrate is a glass bead microsphere of varying weight and size and thegas-emanating stationary support has a complex structure. The stationarysupport provides a gas emanating from a collimated-hole structure heldin place by an alignment spacer. The disclosure describes the use ofshaped collimated hole structures to achieve pneumatic levitation ofnon-porous glass microbeads under low-pressure conditions. Thecollimated hole structure employed in U.S. Pat. No. 4,302,311 is astationary porous gas emitting surface that is shaped with a depressionthat follows the spherical surface topography of the moveablemicrospherical substrate to be levitated. Gas uniformly flows underneaththe spherical substrate during pneumatic levitation. In this case theambient environment in which pneumatic levitation is performed isunusual and the ambient pressure during pneumatic levitation is below500 mTorr—in other words, the pneumatic levitation was performed underreduced pressure conditions. The collimated-hole structure providesmultiple parallel gas jets that are used for pneumatic levitation of themicrospherical substrates and the gas-emanating collimated-holestructure is “dimpled”—meaning that is has depressions in which theglass microspheres sit. The “dimpled” structure can be hemispherical,cylindrical, or conical. The height of the microspherical substrateabove the bottom of the dimple is monitored during pneumatic levitation.The parallel gas jets from the collimated hole structure as well asphysical barriers around the gas emitting depressions help keep themicrospherical substrates in a stable position during pneumaticlevitation and the reactive fluid comprised of a sputtered flux of metalspecies employed for depositing metal films on the levitatingmicrospherical substrates is incident normal to the collimated holestructure, directly opposing the fluid flow of the levitating jets fromthe collimated hole structure. The “dimples” of the gas emanatingcollimated hole structure—meaning the depressions in which the glassmicrospheres sit—are actually a means of providing a physical stop tokeep the spherical substrate in place during pneumatic levitation. Thealignment spacer also provides an additional second physical stop thatkeeps the microspheres in place during pneumatic levitation. U.S. Pat.No. 4,302,311 is an example of managing the reactivity of a fluid flowin a fluid delivery system by means of opposing fluid flows that preventcontact between a reactive fluid and a critical component of the fluiddelivery system used for substrate levitation. It is disclosed in thescientific literature and the levitation art dating prior to that ofU.S. Pat. No. 4,302,311 that spherical objects will exhibit stablelevitation with rotation in a directional gas flow of sufficientvelocity and volumetric flow.

U.S. Pat. No. 4,378,209 by Berge, Oran, and Theiss titled “Gas levitatorhaving fixed levitation node for container-less processing” discloses amethod and apparatus for processing spherical objects during pneumaticlevitation where the levitation is accomplished by use of an “elongatedlevitation tube having contoured interior in the form of convergentsection 12, constriction 15, and divergent section 14 wherein thelevitation node 16 is created”. The elongated levitation tube withlevitation node is disclosed to be suitable for containerless processingof pneumatically levitated spheres and right circular cylinders. Thewalls of the elongated levitation tube in U.S. Pat. No. 4,378,209provide physical stops and a means of confinement of the sample duringestablishment of pneumatic levitation in the levitation node of theapparatus. It is known in the open scientific literature and the art offluidic levitation that solid spherical objects can be stably levitatedin a fluidic flow of sufficient velocity and volumetric flow when thespherical object is allowed to freely rotate in the flow.

U.S. Pat. No. 4,378,209 further discloses the use of an additionalconcentric tube within the elongated levitation tube that can beemployed for various purposes such as supplying solid material to thelevitated object or supplying an additional fluid flow whose initialflow direction opposes the fluid flow of the main elongated levitationtube. U.S. Pat. No. 4,378,209 is an example of managing the reactivityof a fluid flow from a fluid delivery system by employing opposing fluidflows during fluidic levitation in order to control contact between areactive fluid and components of the fluid delivery system used forsubstrate levitation.

U.S. Pat. No. 4,969,676 titled “Air pressure pick-up tool” by LaMagnadiscloses a modification of the Bernoulli type pick-up tool disclosed byMammel in U.S. Pat. No. 3,466,079. The improvement disclosed in U.S.Pat. No. 4,969,676 is the inclusion “of a cavity in the major surface ofthe head member surrounding the air passage . . . ” of the devicedisclosed in U.S. Pat. No. 3,466,079. The cavity on the bottom surfaceof the Bernoulli type pick-up is proximate to the exit orifice where gasis injected into the gap between the pick-up surface and the substratesurface and is believed to produce more uniform radial flow of fluidalong the substrate surface. U.S. Pat. No. 4,969,676 discloses the useof physical stops to restrain lateral movement of the substrate duringfluidic levitation of the planar substrate.

U.S. Pat. No. 5,067,762 titled “Non-contact conveying device” by Akashidiscloses a Bernoulli type pick-up tool comprised of a novel gasinjection cavity and rim whereupon increased Bernoulli lift force isproduced at the levitating substrate surface during fluid flow. U.S.Pat. No. 5,067,762 describes an apparatus comprised of a “cushion-vacuumroom” and a Bernoulli surface. U.S. Pat. No. 5,067,762 specificallydiscloses a “non-contact conveying device that has a guide means toprevent lateral movement of articles.” The guide means disclosed in U.S.Pat. No. 5,067,762 comprises “a plurality of bars extending radially andhaving stoppers extending below the plane in which the Bernoulli surface4 exists. Also some bars 10a may have steps 10b to contact certain partsof the surface of the article B where contact is acceptable. Article Bis prevented from lateral movement and can be placed at a desiredposition” (col. 7, lines 39-43). Article B is the substrate. U.S. Pat.No. 5,067,762 thus discloses the use of physical stops to restrictsubstrate motion of planar substrates during fluidic levitationemploying gaseous fluids.

WO 96/29446 entitled “Chemical Vapor Deposition of Levitated Objects” byWest and Criss discloses an apparatus and a method for depositionrhenium metal films on spherical carbon moveable substrates that arepneumatically levitated under reduced pressure conditions. The gasemanating stationary support is a funnel shaped and provides physicalstops that can prevent the pneumatically levitated spherical moveablesubstrate from moving out of the levitating gas flow. It is known in theopen scientific literature and in the patent art dating prior to WO96/29446 that a solid spherical object can be stably levitated in afluidic flow when the spherical object is allowed to rotate in a gasflow of sufficient volumetric flow and velocity.

U.S. Pat. No. 5,096,017 by Rey and Merkeley titled “Aero-acousticlevitation device and method” discloses the levitation of the specimenobject using a concentrated flow of gas and stabilizing the position ofthe specimen object using acoustic positioning forces generated byacoustic waves during heating and cooling of the specimen object. Thespecimen object is spatially confined at the nodes generated by theinteracting acoustic positioning forces thus producing stable levitationof the specimen object and achieving container-less processing of thespecimen object during heating and cooling of the specimen object.Although it is known in the art that solid spherical objects can bestably levitated in a fluidic flow when the spherical object is allowedto rotate in a fluid flow of sufficient volumetric flow and velocity,U.S. Pat. No. 5,096,017 discloses an apparatus and method by whichnon-rigid spherical objects, such as liquid or molten liquid drops, canbe stably levitated.

U.S. Pat. No. 5,492,566 by Sumnitsch titled “Support for disk-shapedarticles using the Bernoulli principle” discloses an apparatus forsupporting disk shaped articles. The surface of the apparatus iscircularly shaped and equipped with an annular gas ejection nozzle thatprovides gas flow of sufficient velocity to pneumatically levitate asubstrate facing the support surface. The lateral motion of thesubstrate during pneumatic levitation is prevented by the introductionof at least one mechanically fixed elastic support pad or at least onemechanically fixed elastic support structure located on the surface ofthe apparatus that contact the opposing substrate surface when thesubstrate is pulled down towards the apparatus surface by the Bernoullieffect when gas is ejected from the annular nozzle. U.S. Pat. No.5,492,566 does not disclose a non-contact method for stabilizing theposition during pneumatic levitation. The substrate contacts an elasticpad during pneumatic levitation in U.S. Pat. No. 5,492,566.

U.S. Pat. No. 5,967,578 by Frey titled “Tool for the contact-freesupport of plate like substrates” discloses a tool for handlingplate-like circular wafers equipped with a circular “dynamic” gasdistribution chamber and an annular gas ejection nozzle that providesgas flow of sufficient velocity to pneumatically levitate a substratefacing the support surface. The lateral motion of the substrate duringpneumatic levitation is prevented by the introduction of at least twoguiding means arranged at spaced locations to each other and extendingvertically with respect to the surface of the tool at a distance besidesthe gas emitting annular slit. “These guiding means are arranged in sucha way as to provide “contact points” or “contact lines” for the outerperiphery of the wafer to be treated”. The guiding means are intended torestrain the lateral motion of the substrate during pneumatic levitationwhen the tool is employed for supporting a circular plate likesubstrate.

U.S. Pat. No. 7,328,617 B2 titled “Air levitation apparatus withneutralization device and neutralization methods for levitationapparatus” by Miyachi, Nishikawa, and Suzuki discloses an air levitationdevice employed to transport plate shaped work, such as thin plates ofmaterial like glass, wherein the air levitation device comprises a meansof air ionization and a levitation apparatus providing a plurality ofair jets as a means of levitating the plate shaped work. The means ofair ionization is a corona discharge device employing at least oneneedle-shaped electrode. The air levitation apparatus of U.S. Pat. No.7,328,617 B2 is intended as a means of substrate transport, bothallowing motion of the plate and providing a means of motion to theplate shaped work and thus the apparatus does not have a function ofproviding air levitation or pneumatic levitation wherein the plateshaped work is motionless or laterally restricted in motion.

U.S. Publication No. 2007/0215437 A1 titled “Gas bearingsubstrate-loading mechanism process” by Cassagne discloses pneumaticlevitation of a thin plate-like substrate by means of flotation on alayer of gas produced by a plurality of gas emitting ports. Adjacent tothese ports and spatially intermingled with the gas emitting ports arevacuum port employed to keep the thin plate-like substrate stationarywhen required. U.S. Publication No. 2007/0215437 A1 teaches the use ofrobotic grippers—also called a “clamping system”- or a “pushing/pulling”system to restrict and control the normally unimpeded motion of thesubstrate on the frictionless gas layer. U.S. Publication No.2007/0215437 A1 teaches that a system of mechanical restraints isnecessary when employing fluidic levitation to levitate a substratewhile restricting undesired lateral motion of the substrate.

U.S. Publication No. 2012/0110528 A1 titled “Device and method for thecontactless seizing of glass sheets” by Herfert discloses an apparatusfor moving large glass sheet with no physical contact to the glass sheetwhere the gripping force is supplied by balancing a suction forcesupplied by reduced pressure in a cup with a positive pressure suppliedby atmospheric pressure ultrasonic waves. No physical restraints torestrict the movement of the levitated glass sheet are disclosed. Theapparatus of U.S. Publication No. 2012/0110528 A1 effectively levitatesthe large glass sheet at several different locations on the glass sheetsubstrate and as a result levitates the entire sheet. In the absence ofconstant adjustment of the levitation position or the use of physicalrestraints on the perimeter of the substrate, the glass sheet will notremain stationary due to the frictionless nature of the levitationmethod employed and the glass sheet will begin to be transported in amanner similar to U.S. Pat. No. 7,328,617 B2.

U.S. Pat. No. 6,601,888 B2 titled “Contactless Handling of Objects” byMcIlwraith and Christie discloses a method and apparatus for handlinglarge lithographic plates. The disclosed apparatus is a vibrationdampening Bernoulli type pick-up device, similar in concept to thatdisclosed by Mammel in U.S. Pat. No. 3,466,079. U.S. Pat. No. 6,601,888B2 teaches that flexible plate-like objects will vibrate and emit highintensity acoustic signals when levitated using a Bernoulli type pick-updevice and the intensity of the acoustic signals produced duringpneumatic levitation can be reduced by introducing avibration-attenuating surface into the Bernoulli type pick-up deviceover which the fluid must flow during the levitation process. Thevibration-attenuating surface can be prepared by numerous methods,including modifying the surface near the fluid exiting edges of theBernoulli type pick-up device with ridges, fibers, bristles, or otherphysical features that can cause interruption of the fluid flow as thepressure of the fluid equalized with the surrounding medium. U.S. Pat.No. 6,601,888 B2 acknowledges that “preventing lateral movement ofobjects” that are levitated is a problem but does not provide anyteaching or inventive disclosure concerning how to address this problemother than to mention the previously disclosed teaching in the art offluidic levitation concerning the use of physical stops and barriers toprevent substrate motion.

U.S. Pat. No. 8,057,602 B2 by Koelmel et al titled “Apparatus and Methodfor Supporting, Positioning and Rotating a Substrate in a ProcessingChamber” discloses a method and apparatus employing fluids injectedthrough ports on a baseplate support, said fluid contacting a surface ofa substrate to control substrate position and rotation. At least 3 portsadapted to receive a fluid from a flow controller and direct the fluidin different directions are employed and at least a portion of the flowof the fluids from the plurality of ports are adapted to support theweight of the substrate. The fluid flow can be either sub-sonic orsuper-sonic and the advantages of different fluid flow velocities arecontemplated for the purposes of providing momentum transfer to asubstrate supported by a fluid layer of any type, gaseous or condensed,in order to bring the substrate into a desired position. A processcontrol loop for fluid flow to each port based on sensor feedbackindicating the substrate position is contemplated and the processcontrol loop is used to adjust the fluid flow to each port in theplurality of ports in order to stabilize and control the substrateposition. Both software and hardware implementations of the control loopare contemplated. The ports contemplated in U.S. Pat. No. 8,057,602 B2may be employed to add or remove fluid from the volume between thesubstrate and the substrate support base plate. The use of thermal edgebarriers to restrict overall substrate motion and improve processtemperature uniformity is discussed and taught as part of the apparatus.The apparatus described appears complex, requiring control of fluidthrough multiple fluid ports with complicated electrical feedbackcircuits being required. The contemplated invention of U.S. Pat. No.8,057,602 B2 still invokes the use of physical stops called “thermaledge barriers” as an integral part of the apparatus in order to restrictthe unpredictable motion of the substrate motion that can occur whilethe substrate is supported by the essentially frictionless layer offluid, although the invention claims to solve the problem of physicalcontact between the substrate and any proximate apparatus employed toprovide a means of additional processing during substrate handling bythe levitation apparatus.

The scientific literature further discloses additional methods forachieving fluidic levitation with gaseous fluids. Dini, Fantoni, andFailli (G. Dini, G. Fantoni, and F. Failli; “Grasping leather plies byBernoulli grippers”, CRIP Annals, Manufacturing Technology 58 (2009)21-24) disclose the use of several variants of Bernoulli type pick-uptools for use with leather plies. Li, Kawashima, and Kagawa (X. Li, K.Kawashima, and T. Kagawa; “Analysis of vortex levitation”; ExperimentalThermal and Fluid Science, 32 (2008) 1448-1454) disclosed a novelapparatus and method for fluidic levitation which they call “vortexlevitation”. The apparatus for producing vortex levitation is similar tothat disclosed by Akashi in U.S. Pat. No. 5,067,762. As with Akashi, gasis injected into a gas injection cavity—which appears identical to the“cushion-vacuum room” described by Akashi. The gas injection cavity isessentially cup shaped and the gas is injected in the cup at a specificlocation: the vortex levitation cup of Li et al employs a fluid underpressure that is injected tangentially to the walls of the cup shapedgas injection cavity to induce a swirling flow that exits the gasinjection cavity through a rim that functions as a Bernoulli surface. Liet al disclose the use of “a set of vortex cups to achieve betterstability and a larger lifting force” on what appears to be a plateshaped object but no further details are provided. Wu, Ye, and Meng(Particle image velocimetry studies on the swirling flow structure inthe vortex gripper”, Proceedings of the Institution of MechanicalEngineers, Part C, Journal of Mechanical Engineering Science 0(0),(2012) 1-11; DOI: 10.1177/0954406212469323) report a characterization ofthe fluid movement in a modified vortex gripper during vortexlevitation. The modified design investigated by Wu et al introduced aconical frustum in the center of the cup shaped gas injection cavity ofthe vortex levitation apparatus described by Li et al which was used tosimplify particle imaging during levitation.

The scientific article “Levitation in Physics” by E. H. Brandt (Sciencevol. 243, pg. 349-355, 1989) outlines the physical effects allowing forfree floatation of solids and even liquid matter. Among the levitationmethods disclosed are levitation methods employing a variety of meansincluding jets of gas, sound waves, beams of laser light,radio-frequency fields, charged particles in alternating electricfields, magnetic repulsion, flux pinning of superconductors and thelike. Brandt states that “the main problem in the physics of levitationis stability: the levitated body should not slip sideways but should besubjected to restoring forces in all directions horizontally andvertically when it is slightly displaced from its equilibrium position.”Brandt discusses the stable levitation of spheres is a flowing jet ofgas in the section on “Aerodynamic Levitation”, commenting that thereare certain apparatus configurations for aerodynamic levitation ofspherical objects which are essentially independent of orientation andgravity. There is no discussion of aerodynamic levitation, also known aspneumatic levitation, of disc-shaped objects, plate shaped objects andarticles, or other types of planar objects such as planar rectangularshapes, or non-spherical object suggesting that, at the time ofpublication, there is no known method for achieving stable pneumaticlevitation of such an object and preventing the sideways slip andlateral motion of the object during the levitation process withoutphysical contact to the sample or the introduction of some sort ofadditional external restoring force that is imposed upon the intrinsicfluidic forces introduced by the levitation process itself.

Theoretical fluid mechanic analysis of pneumatic levitation processesconcludes that it is impossible to fluidically levitate a disc(workpiece) with a single jet of a gaseous fluid except in one specificconfiguration. A. D. Fitt, G. Kozyreff, and J. R. Ockendon in a papertitled “Inertial Levitation” write in the Journal of Fluid Mechanics (J.Fluid Mech. (2004) vol 508, pp 165-174; page 172 concluding remarks)with respect to moveable substrate levitation with an orthogonal gaseousfluid jet the following: “Of course, if air were blown through a singlehole of sufficient radius in the base plate, levitation could not occurbecause of the pressure drop as the air accelerates in the layer. Infact, it is possible to support a plate by this method by placing thebase plate above the workpiece. It can also be supported in such anupside-down configuration by suction through the base plate, and thistechnique is also used in the glass industry.” Fitt et al. indicate thatpneumatic levitation of planar workpiece or planar moveable substratewhen the fluid emitting baseplate is below the workpiece will not occur.The remarks by Fitt et al. in a peer reviewed scientific journalindicate that a method or apparatus to fluidically levitate a substratein a stable manner with a fluid flow emanating from a support beneaththe substrate is apparently not known and not obvious to those skilledin the art of fluid mechanics.

Pressurized fluid flow devices for the purpose of substrate levitationor flotation on a gaseous layer or gaseous cushion have been integratedinto other technologies specifically for the purpose of preventingphysical contact with a surface of said substrate during transport oralignment. U.S. Pat. No. 5,470,420 describes the use of pressurizedfluid flow devices as a means of handling adhesive labels and preventingcontact with the surfaces of the label. A pressurized fluid flow deviceis employed to support wafer substrates for transport and pre-alignmentprior to electrostatic chucking or placement of the substrate onautomated inspection systems. In these examples, physical stops such asedges, pins, or walls are employed in the apparatus to provide a barrierto lateral movement of the substrate wafer and to stabilize thesubstrate position during substrate transport and subsequent alignmentoperations so that sideways motion of the substrate is prevented whilethe substrate is suspended on the frictionless gaseous layer or cushionlocated between the substrate and the proximate fluid emitting supportcontaining one or more nozzles, gas injection cavities, or orifices thatprovide pressurized fluid between the substrate and the fluid emittingsupport containing at least one fluid emitting nozzle or fluid emittingorifice employed as a means to provide Bernoulli lift.

Levitation processes can be carried out with both compressible andnon-compressible or incompressible fluids. Levitation processes withcompressible fluids are also referred to as pneumatic levitationprocesses or just pneumatic levitation and are commonly achieved throughthe use of gaseous fluids. Common gaseous fluids employed for pneumaticlevitation are air, nitrogen, other inert gases such as argon, and othergases that remain in the gas phase under the conditions encountered bythe gas during pneumatic levitation. Levitation processes withnon-compressible or incompressible fluids are also referred to ashydraulic levitation processes or just hydraulic levitation and arecommonly achieved through the use of incompressible fluids such asliquid phase fluids such as water, various types of specially formulatedoils, or other liquid fluids that remain in the liquid phase under theconditions encountered by the liquid during hydraulic levitation.

Stabilizing Lateral Substrate Movement

Most of the previous efforts directed towards stabilizing the positionof a non-spherical substrate, including plate-like substrates, duringlevitation and preventing lateral movement of the substrate duringlevitation have focused on the use of physical restraints such as wallsand stops to constrain and prevent the lateral motion of the substrateduring levitation. Other efforts to stabilize substrate position andcontrol lateral motion during levitation have employed complicatedschemes for using supplemental fluid flows whose direction must besomehow controlled to introduce appropriate directional correctiveforces on the substrate by transfer of momentum from the fluid used asthe medium for levitation. This complicated process of fluid momentumtransfer to control lateral substrate motion must occur during and inthe presence of the gaseous fluid flow employed as a means of achievingfluidic pneumatic levitation and Bernoulli lift. Such schemes aredifficult to implement, can lead to levitation height instability andpositional oscillation as a result of unstable fluid flows, and requirecomplicated pneumatic control sequences and feedback control loops forexecution.

Examples of non-orthogonal jets and their uses are described by Yokajtyin U.S. Pat. No. 5,470,420 where tilted jets are employed specificallyto transfer momentum from the gaseous fluid flow of the jets so as toinduce lateral movement of the substrate movement during pneumaticallylevitation of the substrate. U.S. Pat. No. 5,470,420 by Yokatjydiscloses the use of arrays of tilted jets, (jets which arenon-orthogonal with reference to the stationary support surface normal),for the purpose of intentionally destabilizing the position of a movablesubstrate and inducing substrate movement in a predetermined direction,either rotationally about an axis or in a specific direction parallel tothe stationary support surface. In U.S. Pat. No. 5,470,420 the moveablesubstrate is a label. According to Yokajty, the gaseous flow from thetilted jet array gives rise to an attractive force between the substrateand the stationary support. In describing the interactions that occurwhen the label is pneumatically levitated by a tilted jet array, Yokajtystates with respect to the action of tilted jet causing pneumaticlevitation that “The flow of gas causes a zone of reduced gas pressureto be formed between the support surface 52 and label 14, in accordancewith the Bernoulli Effect, thereby establishing a pressure differentialacross the label to hold the label in position on a film of gas flowingover the support surface.” In U.S. Pat. No. 5,470,420 it is not clearwhere this pressure differential occurs and, additionally, the specificobjective of the invention is to induce movement of the pneumaticallylevitated substrate so that it can be properly aligned against a set ofstops which physically interrupt the substrate movement. In U.S. Pat.No. 5,470,420 tilted jets are employed specifically to transfer momentumfrom the gaseous fluid flow of the jets so as to induce substratemovement, including rotational movement, during pneumatically levitationof the substrate. The use of tilted jets, either singly or in an array,excludes the possibility of gaseous fluid flow that is symmetrical aboutthe jet; instead, the gaseous fluid flow patterns generated by tiltedjets and tilted jet arrays have strong velocity components which aredetermined by the tilted jet velocity vectors. The flow velocity vectorsgenerated by tilted jets are neither orthogonal nor parallel to theopposing moveable substrate surface. The pneumatic levitationaccomplished by means of tilted jets like those described in U.S. Pat.No. 5,470,420 is sometimes referred to as Bernoulli airflow.

Interestingly, the descriptions by Yokajty in U.S. Pat. No. 5,470,420 ofthe action of orthogonal jets that are found in the description of FIG.10 state that orthogonal jets are used to “blow the label onto thearticle to be labeled” (col. 6 lines 4-6) indicating that according toYokajty, orthogonal jets cannot show attractive forces or pneumaticlevitation of substrates. U.S. Pat. No. 5,470,420 does not teachpneumatic levitation of objects with orthogonal fluid jets. U.S. Pat.No. 5,470,420 does not teach pneumatic levitation of a moveablesubstrate using both tilted jets and orthogonal jets simultaneously.

U.S. Pat. Nos. 5,492,566 and 5,967,578 disclose the use of an annularnozzle comprised of an infinitely large number of tilted jets for thepurpose of producing pneumatic levitation by means of Bernoulli airflowand supporting a moveable substrate 12. Annular nozzles of the typedescribed in U.S. Pat. Nos. 5,492,566 and 5,967,578 are formed when thespacing between a plurality of tilted jets positioned around thecircumference of a circle becomes infinitely small and the plurality oforifices from whence the tilted jets emanate are arranged about thecircumference of a circle in such a manner that projection of eachtilted jet on the gas emanating surface is aligned parallel to a radiusof said circle and the fluid flow of each tilted jet is directed awayfrom the center of the circle. The annular nozzle structure disclosed inU.S. Pat. Nos. 5,492,566 and 5,967,578 produces a symmetric radial flowfield flowing directionally outward and away from the center of theannular nozzle structure and centered around the centroid of the annularnozzle structure. The pneumatic levitation produced by the apparatus inU.S. Pat. Nos. 5,492,566 and 5,967,578 is unstable with respect tolateral movement of the opposing substrate for the reasons cited in U.S.Pat. No. 3,466,079 because it is nearly impossible to center thecentroid of the moveable substrate over the centroid of the annularnozzle structure. Both U.S. Pat. Nos. 5,492,566 and 5,967,578 teach theuse of physical stops to restrain lateral movement of a substratepneumatically levitated by means of an annular nozzle structure.

FIG. 1a illustrates one embodiment of the prior art and shows across-sectional view of a gas-emanating stationary support 12 containinga single fluid collimating conduit, nozzle, bore, or orifice 14 that isin fluid communication with a pressurized manifold (not shown). Orifice14 is hereafter referred to as a fluid collimating conduit 14 and fluidcollimating conduit 14 can be employed with liquids or gasses. A fluidcollimating conduit employed with flowing gas is also called a gascollimating conduit. A fluid collimating conduit employed with flowingliquid is also called a liquid collimating conduit. Dashed normal line16 is normal to an opposing surface of moveable substrate 10 and to thegas-emanating surface of stationary support 12. Upon application ofpressurized fluid to the opening of the fluid collimating conduit 14 influid communication with a pressurized manifold containing pressurizedfluid, the single fluid collimating conduit 14 produces an orthogonaljet emanating from the gas emanating surface. The velocity vector of theorthogonal jet, indicated by the arrows in FIG. 1a , is parallel to thedashed normal line 16 and is normal to a surface of moveable substrate10 and to the surface of gas-emanating stationary support 12. Theorthogonal jet thus impinges in an orthogonal fashion on the opposingsurface of moveable substrate 10. When sufficient fluidic pressure isapplied to produce an orthogonal jet of sufficient pressure andvelocity, the moveable substrate 10 is fluidically levitated but isunstable with respect to lateral motion of the substrate.

FIG. 1b illustrates a different embodiment of the prior art and shows across-sectional view of the stationary support 12 containing the singlefluid collimating conduit 14 that is in fluid communication with apressurized manifold (not shown). Dashed lines 16 are normal to asurface of moveable substrate 10 and to the surface of stationarysupport 12. Upon application of pressurized fluid to the opening of thefluid collimating conduit 14 in fluid communication with a pressurizedmanifold containing pressurized fluid, the single fluid collimatingconduit 14 produces a non-orthogonal jet emanating from the surface ofthe stationary support 12. The single fluid collimating conduit 14,produces a non-orthogonal jet or tilted jet whose velocity vector,indicated by the arrow in FIG. 1b , is not parallel to the dashed normalline 16 and thus is not orthogonal to the surface of moveable substrate10 and is not orthogonal to the surface of stationary support 12. Thenon-orthogonal jet thus impinges in a non-orthogonal fashion on theopposing surface of moveable substrate 10. When sufficient fluidicpressure is applied to the fluid flowing through the fluid collimatingconduit 14 to produce a non-orthogonal jet of sufficient pressure andvelocity, the moveable substrate 10 is fluidically levitated but isunstable with respect to lateral motion of the substrate. As mentionedpreviously, annular nozzles of the type described in U.S. Pat. Nos.5,492,566 and 5,967,578 are formed when the spacing between a pluralityof tilted jets positioned around the circumference of a circle becomesinfinitely small and the plurality of orifices or fluid collimatingconduits 14 from whence the tilted jets emanate are arranged about thecircumference of a circle in such a manner that projection of eachtilted jet on the gas emanating surface is aligned parallel to a radiusof said circle and the fluid flow of each tilted jet is directed awayfrom the center of the circle.

FIG. 2 shows a cross-sectional view illustrating one embodiment of theprior art disclosed in U.S. Pat. No. 5,370,709 (discussed above) that isfrequently employed to address the difficulty of positional instabilityduring fluidic levitation using gasses. U.S. Pat. No. 5,370,709discloses the stationary support 12 containing the single fluidcollimating conduit 14 in fluid communication with a pressurizedmanifold (not shown). The single fluid collimating conduit 14 produces asingle orthogonal jet whose velocity vector indicated by the arrows inFIG. 2 is parallel to the dashed normal line 16 normal to a surface ofmoveable substrate 10 and to a surface 24 of stationary support 12. Theorthogonal jet thus impinges in an orthogonal fashion on the opposingsurface of moveable substrate 10. Stationary support 12 also contains atleast one protruding feature 26 extending above the surface 24 ofstationary support 12 in the direction of moveable substrate 10 and islocated on the surface 24 of stationary support 12 so as to impedehorizontal lateral motion of moveable substrate 10 in the directionparallel to surface 24 of stationary support 12. FIG. 2 illustrates theuse of physical stops, exemplified by protruding feature 26, that iscommonly employed for the purposes of stabilizing the position of themoveable substrate 10 during fluidic levitation so that the moveablesubstrate 10 remains essentially centered over the single fluidcollimating conduit 14 that supplies an orthogonal jet whose velocityvector is parallel to and essentially coincident with a normal to thesurface 24 illustrated by the dashed normal line 16. The location of thefluid collimating conduit 14 in the gas-emanating surface is taken as analignment feature and the moveable substrate 10 is positioned at adesired location relative to the alignment feature. The locations of theprotruding features 26 can also be taken as alignment features forpositioning of the moveable substrate 10 at a desired location beforeinitiating the fluid flow required for pneumatic levitation.

Reactive Chemical Fluid Flow

The presence of reactive chemical substances in the fluid flow duringfluidic levitation can cause complication with equipment operation. Inthis disclosure, the terms reactive chemical substance, chemicallyreactive reagent, reactive reagent, reactive chemical, reactivesubstance, and reactive material will all refer to composition of matterthat is not chemically inert to at least one of the materials ofconstruction of the fluid delivery system. In particular, the presenceof reactive reagents in the orthogonal jet can cause complications withequipment operation. As taught in the art of fluidic levitation forsubstrate processing, reactive materials in the fluid flow can reactwith surfaces of the fluid delivery system and, more importantly, theorifice or orifices or the fluid collimating conduits 14 in the fluidemitting stationary support. The prior art of substrate processing usingfluidic levitation methods is focused on primarily on high temperatureprocesses operating above 500° C. An example of a high-temperatureprocess that can be operated using fluidic levitation is chemical vapordeposition. The art teaches that one approach to controlling thechemical reactivity of the fluid flow is to control the temperature ofthe fluid. This approach is satisfactory if the fluid exhibit chemicalreactivity is strongly temperature dependent; however, more recentdevelopments in substrate processing utilize chemical substances in theprocess fluid flow that are highly reactive with fluid delivery systemmaterials of construction even at room temperature. Highly reactivematerials whose reactivity is appreciable even at room temperature arepresent in the fluid flows that are employed in, for example, atomiclayer deposition processes. Some of the highly reactive materials in thelow temperature fluid flows of atomic layer deposition processes areorganometallic compounds, ozone, metal halides, metal amides, and otherreactive fluid substances.

It is desirable, then, to be able to manage the chemical interactions ofthe highly reactive precursor reagents in the fluid employed for fluidiclevitation. If the fluid delivery system surfaces are chemicallyreactive with the fluid flow then elements of the fluid delivery systemwhose critical dimensions must be maintained for robust system operationmay change over time becoming larger, smaller, or even failingaltogether. The chemical reactivity of the fluid delivery system must,therefore, be managed when non-chemically inert materials are employedas part of the fluid composition of matter in the fluid delivery systemduring fluidic levitation.

Spatially Ordered Fluid-Flow

U.S. Pat. No. 3,368,760 by C. C. Perry titled “Method and apparatus forproviding multiple liquid jets” and U.S. Pat. No. 3,416,730 by C. C.Perry titled “Apparatus for providing multiple liquid jets” bothdescribe methods and apparatus for producing compound liquid fluid flowsand compound liquid jets. Both U.S. Pat. Nos. 3,368,760 and 3,416,730disclose methods and apparatus for compound coaxial jet formation withviscous fluids like liquids, fluid aerosols, and non-gaseous liquid-likeflowable substances including emulsions, dispersions, resins, colloids,suspensions, and composite. Additional fluid-like materials disclosed inU.S. Pat. No. 3,368,760 include gaseous particle suspensions such asthose found when a gas is used to propel a powder through a dischargepassage. U.S. Pat. Nos. 3,368,760 and 3,416,730 teach the use ofpressure comparators to equalize the velocity of the inner primaryliquid jet with the secondary liquid jet velocity in order to preventmixing and turbulence during compound jet formation, teach the use ofswitchable valves to vary the overall composition of the compound jet,and teach the use of concentric fluid emitting nozzles for the purposeof formation of a coaxial compound jet with at least a primary fluid jetand a secondary fluid jet sheath in contact with and surrounding theprimary fluid jet. In general, both U.S. Pat. Nos. 3,368,760 and3,416,730 teach the use of a compound coaxial jet as method to transporta reactive primary fluid by employing a sheath of secondary fluid thatis in contact with and surrounds the primary fluid as a means ofmodulating the reactivity of the primary fluid.

Another disclosure of the concept of compound jet is found in U.S. Pat.No. 4,196,437. U.S. Pat. No. 4,196,437 by C. H. Hertz titled “Method andapparatus for forming a compound liquid jet particularly suited forink-jet printing” describes the use of compound liquid jet to form finedroplets for ink-jet printing applications. The apparatus described byHertz employs a primary stream formed by ejecting under pressure aprimary liquid from a nozzle and then causing the primary stream totraverse a thin layer of a secondary fluid to form a compound liquidstream which breaks up to form a compound jet of fine droplets eachcontaining both the primary liquid and the secondary fluid. U.S. Pat.No. 4,196,437 teaches that the primary fluid, the secondary fluid, orboth the primary and secondary fluid may be reactive fluids. Moreimportantly, the secondary fluid is essentially a stationary fluidthrough which the primary fluid traverses, with the result that thesecondary fluid is dragged along with the primary fluid jet by fluidmomentum interactions. The method of formation of compound jets of thepresent invention does not employ stationary fluid reservoirs or layers,thereby distinguishing it from U.S. Pat. No. 4,196,437. Additionally,the use of compound jets for fluidic levitation is not mentioned oranticipated anywhere in U.S. Pat. No. 4,196,437.

The concept of a compound jet was further articulated in the openscientific literature by Hertz and Hermanrud in 1983 (J. Fluid Mech.(1983), vol 131, pp 271-28′7). Hertz and Hermanrud disclosed “a new typeof liquid-in-air jet generated by a primary fluid jet that emerges froma nozzle below the surface of a stationary (secondary) fluid. Afterbreaking the surface, the jet consists of the central primary jetsurrounded by a sheath of secondary fluid which has been entrained bythe primary jet during its passage through the secondary fluid.” Hertzand Hermanrud call this new type of jet a “compound jet” formed from aprimary and a secondary fluid. According to Hertz and Hermanrud thecompound jet is comprised of a central primary jet of primary fluid thatis surrounded by a sheath of secondary fluid. The article also teachesthat the flow in the compound jet is essentially laminar and that theprimary and secondary fluids can only mix by diffusion. Mixing bydiffusion is a relatively slow process thus the primary and secondaryfluids in the compound jet remain compositionally segregated as the jetpropagates though space.

U.S. Pat. No. 6,377,387 B1 discloses a method for preparing particlesfor use in electrophoretic displays and an apparatus for the formationof compound liquid jets as defined by Hertz and Hermanrud (loc cit) forthe purpose of producing substantially uniformly-sized droplets of afirst phase, the first phase including a fluid and particles, forintroduction into a second phase, for producing substantiallyuniformly-sized complex droplets having a core formed form a firstphase, the first phase including a fluid and particles, and a secondphase that surrounds the first phase as a shell. There is no mention oranticipation of the use of compound jets for fluidic levitationprocesses in U.S. Pat. No. 6,377,387 B1.

WO 02/100558 A1 by Larrell and Nilsson titled “Device for CompoundDispensing” discloses a MEMS based apparatus for dispensing very smallamounts of compound volumes of liquids. The apparatus employs adrop-on-demand type fluid ejector to produce a transient fluid jet for aprimary fluid traversing a stationary fluid reservoir comprised of asecondary fluid to produce a transient compound liquid jet comprised ofa primary fluid stream surrounded by a sheath of secondary fluid thatproduces an encapsulated drop upon breakoff. There is no mention oranticipation of the use of compound jets for fluidic levitationprocesses in WO 02/100558 A1.

U.S. Pat. No. 6,699,356 B2 by Bachrach and Chinn titled “Method andapparatus for chemical-mechanical jet etching of semiconductorstructures” and U.S. Pat. No. 7,037,854 B2 by Bachrach and Chinn titled“Method for chemical-mechanical jet etching of semiconductor structures”disclose the use of at least one liquid jet impinging on a substrate forthe purpose of carrying out various etching operations and processes onvarious semiconductor substrates. In an alternate embodiment U.S. Pat.Nos. 6,699,356 B2 and 7,037,854 B2 disclose the use of at least one gasjet impinging on a substrate for the purpose of carrying out variousetching operations and processes on various semiconductor substrates.The fluidic jets impinge on the surface of a substrate mounted on asubstrate holder, said fluidic jet impinging preferably in anon-orthogonal manner so as to minimize the stagnation area on thesubstrate surface at the jet impingement location. The dual nozzle jetsare described in U.S. Pat. No. 7,037,854 B2 at col. 4, lines 30-37 andU.S. Pat. No. 6,699,356 B2 at col. 4, lines 21-28) “dual nozzle, ornozzle within a nozzle (see FIG. 2), in which a concentric annular outerorifice 201 surrounds a central orifice 203, and discharges a secondaryhigh pressure flow of fluid 205, forming a spray curtain surrounding andcontaining the jet cone 207 for the central orifice, thereby creating amore narrowly focused jet.” Clearly, the jet described in U.S. Pat. Nos.6,699,356 B2 and 7,037,854 B2 is not the same as previous art, but israther a single jet surrounded by a spray curtain of droplets and thefluid discharges from the secondary high pressure fluid flow is not inintimate contact with the primary high pressure fluid flow from thecentral orifice. Unlike the prior art of compound jets as described indetail by Hertz and Hermanrud (loc cit), different jet trajectories forthe secondary high pressure flow of fluid 205 from the annular outerorifice 201 and a primary high pressure jet cone 207 from the centralorifice 203 are used. There is no mention or anticipation of the use ofcompound jets for fluidic levitation processes in U.S. Pat. Nos.6,699,356 B2 and 7,037,854 B2.

U.S. Patent Application Publication No. 2012/0203315 A1 by Ripoll et altitled “Method for producing nanofibres of epoxy resin for compositelaminates of aeronautical structures to improve their electromagneticcharacteristics” describes method for improving the electricalproperties of carbon composite materials by application of layers ofcarbon nanotubes dispersed in epoxy and applied to the carbon compositestructure by deposition of nanofibers produced by electrospinning. Acompound liquid coaxial jet as defined by Hertz and Hermanrud (loc cit)is produced during the electrospinning process where the primary fluidcomprising the interior jet is doped with a sufficient amount of carbonnanotubes or other conductive particles or conductive nanoparticlesexceeding the percolation threshold for electrical conductivity and thesecondary fluid providing a surrounding sheath for the primary fluid isan epoxy resin dissolved in a solvent. During electrospinning, the fieldinduced Taylor cone formation followed by compound nanojet formation andsolvent loss results in the formation of conductive nanofibers depositedon a carbon composite substrate according to the electric field patternsin the deposition system. U.S. Pat. No. 7,794,634 B2 by Ripoll et altitled “Procedure to generate nanotubes and compound nanofibres fromcoaxial jets” further elaborates on the application of coaxial compoundliquid jet for the formation of materials using electrospinning methods.U.S. Pat. No. 7,794,634 B2 teaches a compound fluid jet wherein theprimary fluid is a liquid and the secondary fluid providing asurrounding sheath for the primary fluid is a fluid that solidifiesbefore the compound jet breaks up into drops. The compound jet is U.S.Pat. No. 7,794,634 B2 is formed by means of electrospinning whence thefield induced Taylor cone formation followed by compound nanojetformation and secondary fluid solidification results in the formation oftubular nanofibers when the primary fluid is removed. Additionally, theformation of compound nanotubes is taught when both the primary andsecondary fluids solidify before jet breakup the electrospinning.Further detail on applications of compound jets to the formation ofcapsules and particles for food products is given in U.S. Pat. RE44,508E by Ripoll, Calvo, Loscertales, Bon, and Marquez titled “Production ofcapsules and Particles for improvement of food products”. U.S. Pat.RE44,508 E teaches the use of a coaxial compound jet with a primaryfluid surrounded by a sheath of secondary fluid generated byelectrohydrodynamic forces to produce encapsulated particles upon jetbreakup. The coaxial jet must have at least one conducting fluid for theelectrohydrodynamic jet to form and either the conducting fluid may bethe primary fluid or the secondary fluid. Alternatively, both theprimary and secondary fluids may be conducting and contribute to theformation of the electrified jet during an electrospinning-like process.The secondary fluid is used to encapsulate the primary fluid during bothjet formation and drop formation during jet breakup. U.S. Pat. RE44,508E teaches the use of biocompatible fluids in the coaxial compound jet inan electrospray process to produce biocompatible encapsulated particlesas vehicles for additives in food formulation. There is no mention oranticipation of the use of compound jets for fluidic levitationprocesses in U.S. Patent Application Publication No. 2012/0203315 A1,U.S. Pat. No. 7,794,634 B2, or U.S. Pat. RE44,508 E.

U.S. Pat. No. 8,361,413 B2 by Mott et al titled “Sheath flow device”discloses an apparatus providing a means of forming compound jets wherea primary fluid flow is in contact with and surrounded by a secondaryfluid flow. The device is comprised of a sheath flow system having achannel with at least one fluid transporting structure located in thetop and bottom surfaces situated so as to transport the sheath fluidlaterally across the channel to provide sheath fluid fully surroundingthe core solution. Although U.S. Pat. No. 8,361,413 B2 does not disclosethe use of the sheath flow device for the formation of coaxial orcollinear compound jets, the apparatus described provides a means forproducing compound fluid flows that are useful for compound jetformation and may be used to produce compound jets by, for example,electrohydrodynamic jet formation or other means with suitable fluidformulations.

U.S. Patent Application Publication No. 2014/0027952 A1 by Fan et altitled “Methods for producing coaxial structure using a microfluidicjet” and U.S. Patent Application Publication No. 2014/0035975 A1 byEissen et al titled “Methods and apparatuses for direct deposition offeatures on a surface using a two component microfluidic jet” disclosethe use of compound microfluidic jets for writing patterns on surfacesand for other applications. Both U.S. Patent Application PublicationNos. 2014/0027952 A1 and 2014/0035975 A1 describe a method for producingcoaxial compound jets where a primary liquid is surrounded and incontact with a sheath of a secondary liquid. The surrounding secondarysheath liquid may be chemically inert, chemically reactive with itselfin some manner like a UV curable monomer, or chemically reactive withthe primary liquid in some manner. Methods are described for generatingmulti-component flow for the purposes of producing micro-fluidic jetsthat are used in printing processes. Both U.S. Patent ApplicationPublication Nos. 2014/0027952 A1 and 2014/0035975 A1 describe methodsand apparatus for hydrodynamic focusing of coaxial liquids jets tocontrol the diameter of the primary fluid jet as well as methods forproducing compound coaxial liquid jets that are undisturbed by Rayleighbreakup for extended periods of time so that the compound coaxial jetitself may be employed as a means of mass transport during printing anddeposition processes. There is no mention or anticipation of the use ofcompound jets for fluidic levitation processes in either U.S. PatentApplication Publication 2014/0027952 A1 or 2014/0035975 A1.

Compound Fluid Flows

Compound fluid flows are a type of spatially and compositionally orderedfluid flows. Fluidic levitation of a moveable substrate using anorthogonal jet emanating from a stationary support requires a fluid. Thefluid may be either compressible or non-compressible. An example of acompressible fluid is a gas like air, argon, or nitrogen and an exampleof a non-compressible fluid is a liquid like water or a hydrocarbonfluid. The fluid can have a naturally mixed composition, as in the caseof air, or the fluid can have an intentionally varied composition.Intentionally varied fluid compositions are particularly useful for someapplications of both hydraulic and pneumatic levitation. The use ofintentionally varied fluid compositions requires a means of generatingvaried fluid compositions.

An unconfined stream of rapidly moving fluid is called a jet. A jet maybe formed from either incompressible fluids, such as water, orcompressible fluids such as gasses. A jet of fluid whose cross-sectiondoes not have a uniform chemical composition is called a compound jet.Compound jets can be formed with either compressible or non-compressiblefluids. Compound jets can be formed by several means such as thosedescribed by Hertz in U.S. Pat. No. 4,196,437 for non-compressiblefluids such as liquids. Formation of gaseous compound jets is known tothose skilled in the art of aeronautics and gaseous fluid compound jetsare employed in the study and development of turbine engines foraeronautic applications. The production of gaseous fluid compound jetsis accomplished by several methods, mostly commonly through theformation of coaxial compound jets or collinear compound jets.

Fluid movement is described by the fluid velocity vector that containsthe information about the spatial direction of fluid movement relativeto some reference direction and whose scalar magnitude describes thevelocity of the fluid movement. The fluid flow axis is defined by lineparallel to and superimposed upon the direction of the velocity vectorof the jet taken at the centroid of the cross-section of the jet. Putanother way, the fluid-flow axis is defined by a line passing throughthe centroid of the cross-section of the fluid flow that is parallel toand superimposed upon the direction of the velocity vector at thecentroid of the cross-section of the fluid flow. The fluid flow axisdescribes the movement of the fluid comprising the flow at the centroidof the cross-section of the fluid flow. The fluid flow may be a jet offluid.

Definition of a collinear compound fluid flow: A collinear compoundfluid flow is a compound fluid flow in which fluids of at least twodifferent chemical compositions are present and the chemical compositionof the fluid varies within the cross-section of the fluid flow such thatregions of similar chemical composition flow in parallel paths that arecollinear with the fluid flow axis defined by the direction of fluidpropagation at the centroid of the cross-section of the fluid flow. Thefluid flow may be a jet.

Definition of a coaxial compound fluid flow: A coaxial compound fluidflow is a compound fluid flow in which fluids of at least two differentcompositions are present and the chemical composition of the fluid flowvaries across the cross-sectional area of the fluid flow such thatregions of similar chemical composition are segregated into annuli orinto circular regions, each region being centered around the same fluidflow axis defined by the velocity vector of the fluid flow taken at thecenter of the cross-section of the fluid flow so that one region ofchemical composition is entirely surrounded by a region of differentchemical composition as the regions flow collinearly and simultaneouslyalong an axial direction. The fluid flow may be a jet.

A compound coaxial fluid flow is also a special type of compoundcollinear fluid flow that has a specific annular arrangement ofdifferent chemical compositions. A compound collinear fluid flow mayalso possess at least one characteristic of a coaxial fluid flow suchthat one region of chemical composition may be entirely surrounded by aregion of different chemical composition as the regions flow collinearlyand simultaneously along an axial direction. A difference between acollinear and a coaxial fluid flow is that a collinear jet is notnecessarily completely symmetric about the fluid flow axis whilst thecoaxial jet is always symmetric about the fluid flow axis.

Thus, a compound fluid flow may have both collinear and coaxialcharacteristics as defined by the arrangement of regions of differentchemical composition within the fluid flow relative to the fluid flowaxis as defined by the direction of fluid flow propagation. The chemicaldistribution in a compound fluid flow changes as a function of timebecause of lateral diffusion of chemical species. The degree of lateraldiffusion which results in a redistribution of chemical concentrationsin the cross-section of the fluid flow depends several factors includingtemperature, fluid velocities, and fluid viscosities. In condensedphases and incompressible fluids the lateral diffusion is small. Incompressible fluids near or above atmospheric pressure the lateraldiffusion between regions of differing composition is small. If thedistance that the compound fluid travels is small relative to the fluidvelocity, then the composition and chemical distribution in the compoundfluid flow remains essentially unchanged during the transit time of thefluid flow. This is desirable from a process standpoint as it nowprovides a means for encapsulating reactive precursors with an inertfluid so they can be transported to the moveable substrate surfaceduring the fluidic levitation process.

Atomic Layer Deposition

Atomic layer deposition is a method of forming layers on a substratethat have a well-controlled atomic structure. Such layers can be asingle atom thick. Conventionally, the layers are formed by providing asubstrate in a vacuum chamber and reacting a first gas with thesubstrate surface to deposit a single layer of atoms or molecules on thesubstrate. The first gas is then purged, typically with an inert gassuch as nitrogen, and a second gas is reacted with the layer and thenpurged. By alternately providing gases and purging them, atomic layersof material are built up on the substrate.

Because the atomic layers are so thin, many reaction-purge cycles arenecessary to form a thick structure. In consequence, it is preferred toperform each cycle of the operation very quickly, for example withinmilliseconds. However, the provision and removal of gases in a vacuumtypically requires pumping the gases into and out of the vacuum chamber.This process can take seconds, or even minutes. There is therefore aneed for rapidly providing gases over a substrate surface.

A prior-art method of forming thin films on a substrate using fluid-flowlevitation for atomic-layer deposition is taught in U.S. PatentApplication Publication No. US 2009/0130858 A1, published by Levy, onMay 21, 2009. This approach uses a gas bearing to support a substrate ona head providing spatially alternate flows of inert and reactant gases.The rate at which layers of material are deposited on the substratedepends on the number of alternating gas flows, and hence the head size,and the rate at which the substrate passes over the head.

There is a need, therefore, for an improved apparatus and method forforming thin films on a substrate using atomic layer deposition that iscompatible with existing equipment, provides fast and uniform dispersionof a gas over a substrate in a chamber, and prevents unwanted reactionson chamber surfaces.

SUMMARY OF THE INVENTION

The present invention provides an improved structure, apparatus, andmethod for forming atomic layers on a substrate that is compatible withexisting substrates, provides fast and uniform dispersion of a gas overa substrate, prevents substrate defects and deposition defects, andprevents unwanted reactions on chamber surfaces.

According to an aspect of the invention, a thin film deposition systemfor depositing a thin film on a moveable substrate using atmosphericpressure atomic-layer deposition includes a chamber and a moveablesubstrate having a levitation stabilizing structure located on themoveable substrate that defines an enclosed interior impingement area ofthe moveable substrate. A stationary support, located in the chamber,supports the moveable substrate. The stationary support extends beyondthe enclosed interior impingement area. A pressurized-fluid sourceprovides a fluid flow through the stationary support that impinges onthe moveable substrate within the enclosed interior impingement area ofthe moveable substrate sufficient to levitate the moveable substrate andexpose the moveable substrate to the fluid while restricting the lateralmotion of the moveable substrate with the levitation stabilizingstructure.

BRIEF DESCRIPTION OF THE DRAWINGS

While the description of the invention discloses specific subject matterof the present invention, it is believed that the invention and itsassociated concepts and extensions will be better understood from thefollowing description when taken in conjunction with the accompanyingdrawings, wherein:

FIGS. 1a and 1b are representative cross-sectional views of a moveablesubstrate and a gas-emanating support known in the prior art;

FIG. 2 is a cross-sectional view of a gas-emanating support withphysical stops and a moveable substrate known in the prior art;

FIG. 3 is a cross-sectional view of one embodiment of the inventionincluding a substrate with a levitation stabilizing structure fabricatedthereupon;

FIG. 4 is a cross-sectional view of one embodiment of the inventionincluding a substrate with a levitation stabilizing structure fabricatedthereupon positioned on a gas emanating support;

FIGS. 5a-5h are plan views of different embodiments of levitationstabilizing structures fabricated upon substrates of arbitrary shapewherein the levitation stabilizing structure is circle, an oval, or aconcave or convex polyhedral shape;

FIG. 6a-6e show views of a substrate; and in particular, FIG. 6a is across-sectional view of a non-planar substrate and a gas emanatingsupport; 6 b is a cross-section showing a spherical substrate upon whicha levitation stabilizing structure has been fabricated and a gasemanating support; 6 c is a cross-section showing a spherical substrateupon which a levitation stabilizing structure has been fabricated andanother embodiment of a gas emanating support; 6 d is a plan view normalto the spherical substrate showing a circular levitation stabilizingstructure; and 6 e is a plan view normal to the spherical substrateshowing a pentagonal levitation stabilizing structure;

FIGS. 7a-7b show views of a levitation stabilizing structure; and inparticular, FIG. 7a is an isometric view of a levitation stabilizingstructure on a substrate wherein the levitation stabilizing structure isa convex polyhedral shape; and FIG. 7b is a plan view of a levitationstabilizing structure on a substrate wherein the levitation stabilizingstructure is a convex polyhedral shape;

FIG. 8 is a cross-sectional view showing a substrate with a multilayerlevitation stabilizing structure wherein the levitation stabilizingstructure further includes an adhesion promoting layer;

FIG. 9 is a cross-sectional view showing a substrate, with a multilayerlevitation stabilizing structure wherein the levitation stabilizingstructure further includes an adhesion promoting layer and a depositioninhibiting layer;

FIG. 10 is an illustration of a levitation stabilizing structureincluding structures within the interior impingement area according toan embodiment of the present invention;

FIG. 11 is a cross-sectional view of the prior art for delivering areactive fluid flow during fluidic levitation;

FIG. 12 is a cross-sectional view of one embodiment of an inventiveapparatus for delivering a reactive fluid flow during fluidiclevitation;

FIGS. 13a-13c show views of a non-planar substrate with a levitationstabilizing structure; and in particular, FIG. 13a is a cross-sectionalview of a non-planar substrate with a levitation stabilizing structureand a fluid emitting stationary support; FIG. 13b is a plan view of anon-planar substrate with an annular shaped levitation stabilizingstructure; and FIG. 13c is a plan view of a non-planar substrate with asymmetric polyhedral shaped levitation stabilizing structure;

FIG. 14 is a flow chart describing the steps of one embodiment of themethod for dosing the surface of a substrate with a chemically reactivematerial during fluidic levitation of the substrate;

FIGS. 15a-15d show views of a coaxial fluid delivery tube; and inparticular, FIGS. 15a and 15b are views of coaxial fluid delivery tubes;FIGS. 15c and 15d are cross-sections of the compound fluid flowing fromthe outlet of the coaxial fluid delivery tubes of 15 a and 15 b;

FIG. 16 is a view of a coaxial compound fluid flow delivery assembly forforming and controlling the composition of coaxial fluid flows;

FIG. 17 is a cross-sectional view of an apparatus for fluidic levitationof a moveable substrate with levitation stabilizing structure utilizingcoaxial compound fluid flows to control the fluid composition;

FIGS. 18a-18d show views of a collinear fluid delivery tube; and inparticular, FIGS. 18a and 18b are views of collinear fluid deliverytubes; FIGS. 18c and 18d are cross-sections of the compound fluidflowing from the outlet of the collinear fluid delivery tubes of 18 aand 18 b;

FIG. 19 is a cross-sectional view of an apparatus to control thecomposition of matter of a collinear compound jet;

FIGS. 20a-20c show views of an array of collinear fluid delivery tube;and in particular, FIGS. 20a and 20b are views of an array of collinearfluid delivery tubes; and FIG. 20c is a cross-sectional view of anapparatus for the formation of collinear compound fluid flows;

FIG. 21 is a cross-sectional view of an apparatus to control thecomposition of matter of a collinear compound jet during fluidiclevitation of a substrate with an orthogonal jet emitting from thesurface of a stationary fluid emanating support, said substrate having alevitation stabilizing structure;

FIG. 22 is a cross-sectional view of an apparatus for carrying out themethod of dosing the surface of a substrate during fluidic levitation,said substrate having a levitation stabilizing structure, by controllingthe composition of matter of a compound jet during fluidic levitation ofsaid substrate with an orthogonal jet emitting from the surface of astationary fluid emanating support;

FIG. 23 is a schematic illustration of a fluid delivery system useful inthe present invention;

FIGS. 24a-24g show illustrations of a substrate and thin-filmstructures; and in particular, FIGS. 24a, 24c, 24e, and 24g areillustrations of a substrate and thin-film structures sequentiallydeposited using the levitation stabilizing structures of FIGS. 24b, 24d,and 24f and the system of the present invention; FIG. 24a is anillustration of a substrate useful in the present invention; FIG. 24b isan illustration of a levitation stabilizing structure that is useful todeposit the structure illustrated in FIG. 24c ; FIG. 24d is anillustration of a levitation stabilizing structure that is useful todeposit the structure illustrated in FIG. 24e ; and FIG. 24f is anillustration of a levitation stabilizing structure that is useful todeposit the structure illustrated in FIG. 24 g;

FIG. 25 is an illustration of an embodiment of a flow control structureproximate to a stationary fluid emitting support; and

FIG. 26 is an illustration of an embodiment of a flow control structureproximate to a stationary fluid emitting support;

FIG. 27 is a cross-sectional view of one embodiment of the inventionincluding a substrate with a levitation stabilizing structure fabricatedthereupon positioned on a gas emanating support wherein the stationarysupport contains a plurality of fluid collimating conduits;

The figures are intended to represent the elements of the invention andthe positional relationship between elements of the invention. Theelements of the invention have been represented using relativedimensions that are felt to best illustrate the elements of theinvention and may not correspond to the actual dimension of the elementsas the invention is practiced.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed toward methods, equipment, andstructures for depositing atomic layers on a moveable substrate byemploying Bernoulli effects to fluidically levitate the moveablesubstrate over a stationary support through which fluid will flow. Theinvention includes a levitation stabilizing structure that is employedduring fluidic levitation by attaching the levitation stabilizingstructure to the surface of the levitated moveable substrate. Thepresent invention also includes a method for achieving stable fluidiclevitation of a moveable substrate with one or more orthogonal jets, andoptionally one or more non-orthogonal jets, where the lateral movementof the moveable substrate during the fluidic levitation process iscontrolled by employing a levitation stabilizing structure on thesurface of the substrate.

The present specification also teaches the utility and advantages offluidic levitation during substrate processing. Some of the advantagesof fluidic levitation during substrate processing include contact-lesssample processing, rapid heating and cooling of the substrate due to theisolation of the sample by the fluidic flow, particle cleanliness andlow particle defectivity, improvement in removal of fluid processproducts, and improvements in process uniformity. In an embodiment, thepresent invention discloses a method for providing stable fluidiclevitation that employs a single orthogonal jet and optionally one ormore tilted jets. In other embodiments, multiple jets are used.

A useful embodiment of the present invention provides a non-contactmethod for achieving positional stability of a moveable substrate duringfluid levitation wherein the fluid is either a gas or a liquid. Inparticular, the invention provides a non-contact method for achievingpositional stability of a moveable substrate during fluid levitationwherein the lateral motion of a planar substrate is controlled duringfluid levitation and the fluid is a gas or a liquid. In a furtherembodiment, the invention provides a non-contact method for achievingpositional stability of a substrate during fluid levitation wherein thelateral motion of planar plate-shaped substrates is controlled duringfluid levitation and the fluid is a gas or a liquid. An alternativeembodiment provides a non-contact method for achieving positionalstability of a pneumatically levitated substrate floating on a gaseousfluid layer produced by a collimated fluid gaseous jet during themoveable substrate processing for the purpose of reducing the substratedefectivity incurred as a result of processing. In yet anotherembodiment, the invention provides a method of moveable substratehandling wherein the defectivity whose root causes are attributed toeither repeated physical contact with any portion of the moveablesubstrate surface or to particles generated as a result of physicalcontact with the moveable substrate can be minimized or eliminatedduring substrate processing, the substrate processing includingsubstrate transport, substrate handling, substrate storage, as well asother processing sequences such as, for example, deposition, etching,and cleaning. The invention also provides a method for achievingpositional stability of a moveable substrate levitated on a gaseousfluid layer produced by a collimated fluid gaseous jet wherein themethod is compatible with normal fabrication methods and workflowemployed in the manufacture of integrated circuits and the like.Furthermore, the invention provides a non-contact method of achievingpositional stability of a moveable substrate levitated on a gaseousfluid layer produced by a gaseous jet wherein a substrate of variableshape, for example, circular or non-circular, planar or non-planar isemployed. An additional embodiment provides a non-contact method ofachieving positional stability of a substrate levitated hydraulically orpneumatically on a fluid layer produced by a fluid jet wherein themethod is compatible with miniaturization for the purpose of integratingsaid method of positional stabilization of a substrate during fluidiclevitation into microelectromechanical systems for the purpose ofproducing novel and hitherto unknown miniaturized pneumatic or hydraulicdevices as well as novel micromechanical and micro-fluidic devicesoperating with liquids or gases. In yet another embodiment, theinvention provides a method for utilizing and controlling fluid energyand fluid flow on a miniature or microscopic scale by either passive oractive means.

A substrate is an object of definite shape and volume comprised of asurface together with the volume enclosed by the surface. In oneembodiment, a substrate is an object of definite shape and volume thathas at least one surface. A solid substrate is an object of definiteshape and volume, not liquid or gaseous, comprised of a surface togetherwith the volume enclosed by the surface. In one embodiment the volume ofa substrate enclosed by the substrate surface can be comprised of anon-commingled mixture of liquids, gases, or solids. In an embodimentthe volume of a substrate enclosed by the substrate surface can becomprised of a commingled mixture of liquids, gases, or solids. Inanother embodiment the volume of a substrate enclosed by the substratesurface can be comprised of a mixture of liquids, gases, and solids. Inanother embodiment, the volume of a substrate enclosed by a substratesurface can be comprised of a mixture of solids and gases. An example ofa commingled mixture of a solid and a gas is a solid with holes,bubbles, tunnels, or channels in it where the holes, bubbles, tunnels,or channels are filled with a gas. In one embodiment, the volume of asubstrate enclosed by a substrate surface can be comprised of a mixtureof solids and liquids. An example of a commingled mixture of a solid anda liquid is a solid with holes, bubbles, tunnels, or channels in itwhere the holes, bubbles, tunnels, or channels are filled with a liquid.In a further embodiment, the volume of a substrate enclosed by asubstrate surface can be comprised of a commingled mixture of gases andliquids. In an embodiment, the volume of a substrate enclosed by asubstrate surface can be comprised of a commingled mixture of at leastone liquid. An example of a liquid that can be used to form a substrateis supercooled liquid like a glass. Another example of a liquid that canbe used to form a substrate is a gel. In a further embodiment, thevolume of a substrate enclosed by a substrate surface can be comprisedof a commingled mixture of gases and liquids. An example of a commingledmixture of gases and liquids is a glass with bubbles in it. The volumeof a substrate enclosed by a substrate surface can be comprised of acommingled mixture of solids. The volume of a substrate enclosed by asubstrate surface can be comprised of a non-commingled mixture ofsolids. In one embodiment of a substrate, the mixture of solids in thevolume enclosed by a substrate surface can be layered and comprised ofone or more layers of solid material overlaying and in contact with oneanother. In an embodiment of a substrate, a substrate comprised of amixture of layered solids in the volume of substrate enclosed by thesubstrate surface has existing layers. Thin films on a substrate areexisting layers.

For the purposes of the invention the term “moveable substrate” refersto a substrate that undergoes positional displacement during fluidiclevitation upon exposure to a fluidic flow employed for the purpose ofinducing fluidic levitation of the substrate and opposing the force ofgravity during said levitation state. The term “stationary support”refers to a stationary fluid emitting element that is employed for thepurpose of supplying a fluidic flow, said fluidic flow being employedfor the purpose of inducing fluidic levitation of the moveable substrateand producing fluidic forces opposing the force of gravity when themoveable substrate is in a levitated state. The term “support duringlevitation” means that the moveable substrate can be levitated by fluidflow emanating from the stationary support so that gravitational forceon the moveable substrate is opposed by the force of a fluidic flow.When the stationary support located in the chamber supports the moveablesubstrate during levitation, the fluid flow causes the moveablesubstrate to levitate, forming a gap through which fluid can flowbetween at least a portion of the stationary support and a portion ofthe moveable substrate so that the flowing fluid impinges on at least aportion of the substrate to expose the substrate portion to the fluid.

In contrast to moveable substrates, conventional substrates are fixed inposition during processing, for example, using mechanical restraints,vacuum chucks, or electrostatic chucks.

As used herein, the terms “reactive chemical substance”, “chemicallyreactive reagent”, “reactive reagent”, “reactive chemical”, “reactivesubstance”, and “reactive material” will all refer to composition ofmatter that is not chemically inert to at least one of the materials ofconstruction of the fluid delivery system. A reactive fluid flow isfluid flow containing and comprised of at least one composition ofmatter that is not chemically inert to at least one of the materials ofconstruction of the fluid delivery system or a surface of the moveablesubstrate. A reactive fluid flow can be comprised of a chemicallyreactive gaseous fluid. A reactive fluid flow can be comprised of achemically reactive condensed fluid like a liquid. A reactive fluid flowcan be comprised of a chemically reactive aerosol comprised of solid orliquid particles dispersed and intermingled in a gas. A reactive fluidflow can be comprised of a chemically reactive dispersion comprised ofsolid particles dispersed and intermingled in a liquid. A reactive fluidflow can be comprised of a chemically reactive dispersion comprised oftwo immiscible liquids dispersed and intermingled to form a compositeliquid fluid.

In general, levitation is the condition that occurs when the force ofgravity on a movable substrate has been equaled or exceeded by anexternal opposing force. Fluidic levitation is the condition where theforce of gravity on a substrate has been equaled or exceeded by anexternal opposing force supplied by a fluid such as a gas or liquid. Theterm “support during levitation” means that the moveable substrate canbe levitated by fluid flow emanating from the stationary support throughwhich fluid will flow so that gravitational force on the moveablesubstrate is opposed by the force of a fluidic flow. As used here,pneumatic levitation using a gaseous fluid, that is—a compressible gasphase fluid, is the condition occurring when the force of gravity on asubstrate has been equaled or exceeded by an external opposing forceproduced by application of a gaseous fluid and its associated flowproximate to the substrate surface, the substrate being rigid orflexible, and the substrate being held and suspended proximate to astationary gas emitting support through which fluid will flow andseparated from the stationary gas emanating stationary support only by agaseous layer of fluid which occupies the volume between the movablesubstrate and the stationary gaseous fluid emitting support. Thesubstrate is a movable object responding to both the force of gravityand to the external pneumatic forces produced by pneumatic flow, saidpneumatic flow occupying the volume between the substrate and thestationary fluid emanating support. In this disclosure the substrateparticipating in the process of fluidic levitation is also called themoveable substrate because it exhibits motion in response to theapplication of pneumatic force or fluid force from the fluid emanatingfrom the fluid emitting stationary support. The term “stationarysupport” means that the application of pneumatic force as a result ofthe initiation of gas flow from the stationary gaseous fluid emittingsupport through which fluid will flow results fluidic levitation byvirtue of movement of the substrate, not by movement of the fluidemanating support. Of course, it is possible that the stationary gasemitting support can be transported or become movable while a substrateis fluidically levitating thereupon, resulting in simultaneous movementof both the fluidically levitating substrate and the stationary support.

Pneumatic levitation can occur for substrates of many different shapesand many different chemical compositions. A notable example is thepneumatic levitation of a spherical object often exemplified by thepneumatic levitation of a rotating billiard ball in a high velocityproximate gas stream. An industrial application of pneumatic levitationis the handling and transport of essentially planar objects such aslabels, webs, and sheets of various materials, including sheets ofglass. Pneumatic levitation is also applied to the handling, transport,and positioning of diverse materials such as thin plate-like circularshaped wafers of silicon and large glass sheets for the purpose ofminimizing and eliminating physical contact with the surfaces of themovable pneumatically levitating substrate as well as to minimizeparticle contamination of delicate surfaces such as optical films orintegrated circuits that have been fabricated on the surfaces of themovable substrates.

There are several methods for achieving pneumatic levitation of amovable substrate and providing a gaseous fluid proximate to the movablesubstrate using a stationary gaseous fluid emitting surface for thepurpose of pneumatic levitation and providing a gaseous cushion orgaseous layer upon which the movable substrate can be supported orfloated, such that the force of gravity on the non-stationary substrateis overcome by an opposing pneumatic force and there is no physicalcontact between the opposing substrate and the surface of the stationaryfluid emitting support assembly employed as a means for providing thefrictionless gaseous layer.

The gaseous cushion or gaseous layer upon which the movable substratecan be supported or floated during pneumatic levitation can be achievedwith a variety of gas phase fluids when suitable conditions are used. Itis preferable that the gaseous fluid employed for the purpose ofachieving pneumatic levitation possesses the property that the gas doesnot undergo phase transitions and condense to either a liquid or a solidbut instead remain as a gas in the gas phase under the temperature andpressure conditions employed during the process of pneumatic levitation.The temperature and pressure conditions encountered and experienced by afluid during the process of pneumatic levitation conditions can involvepressure and temperature excursions leading to gas temperatures andpressures above and/or below standard temperature and pressure (273.15Kand 1 atm). It is recognized that phase changes of a gaseous fluid thatcan occur upon exposure to the varying temperature and pressureconditions encountered during pneumatic levitation can result inunpredictable pneumatic levitation phenomena. It is desirable that theone or more gaseous fluids employed for pneumatic levitation have theproperty that sufficient gas remains in the gas phase to sustainpneumatic levitation during any temperature and pressure excursionsexperienced by the gaseous fluid during the pneumatic levitationprocess. Typical gas phase fluids employed for pneumatic levitationinclude but are not restricted to air, any gas that is a component ofair such as nitrogen, hydrogen, helium, neon, argon, krypton, carbondioxide, and the like; mixtures of gases that are components of air;organic compounds, organometallic compounds, and inorganic compounds aswell as other chemical substances and volatile mixtures thereof thatexist is the gaseous phase under pneumatic levitation operatingconditions; gas phase mixtures comprised of organic, organometallic, orinorganic gas phase compounds with gases that are components of air, andthe like.

The local surrounding fluid pressure proximate to both the moveablesubstrate and stationary support is called the ambient fluid pressure orjust the ambient pressure. The fluid environment can be either a gaseousfluid or a condensed fluid like a liquid and is preferably the samemedium as employed for fluidic levitation. Additionally, elements of themoveable substrate that may not be opposing the stationary support mayalso experience ambient pressure. For example, a portion of a web ofpolymer can be pneumatically levitated and the remainder of the web,which is an element of a moveable substrate that is not opposing thestationary fluid emitting support and is not undergoing pneumaticlevitation, still may experience ambient pressure. When the moveablesubstrate and stationary support are placed inside a chamber as part ofan apparatus, the surrounding or ambient pressure of the moveablesubstrate and stationary support, that is—the prevailing fluid pressureproximate to both the moveable substrate and the stationary support—mayrange from the millitorr region to pressures greater than 2 or more bar.Fluidic levitation employing either pneumatic or hydraulic levitationdoes not require a specific ambient pressure for operation, as has beendemonstrated through the many examples reported in the art. For thisreason there is not a preferred ambient pressure specificationassociated with fluidic levitation. In the case of pneumatic levitation,the main ambient pressure requirement is that the ambient conditionsfall within the pressure regime required for the gaseous phase to remaingaseous. Similarly, in the case of hydraulic levitation, the mainambient pressure requirement is that the ambient conditions fall withinthe pressure regime required for the condensed fluid phase to remain asa condensed fluid.

In one embodiment or configuration, the pneumatic layer producing thegravity-opposing pneumatic force, (also called the pneumatic fluidlayer, the fluid layer, the gaseous fluid layer or the gaseous layer),can be provided by a stationary assembly or stationary support throughwhich gaseous fluid will flow with a surface in such a way that a gasflow is uniformly distributed over the entire area underneath themoveable substrate using, for example, a porous surface through whichgas can flow. A porous surface has spaces, holes, or other featuresthrough which a fluid may pass that are distributed over the surfacewherein the surface is uniformly susceptible to the penetration offluids. For example, two fluid filled chambers separated by a poroussurface are in fluid communication in a uniform manner over the entiresurface area of the porous surface. A porous surface is, therefore, asurface having the property of uniform fluid transport at all locationson the surface. The substrate surface facing the porous gas emittingsurface can be planar, non-porous, and essentially featureless or it canbe shaped in some manner to conform in topographical manner topre-existing 3 dimensional features of the porous gas emitting surface.The substrate surface facing the gas emitting surface is also called thesubstrate surface opposing the porous gas emitting surface of thestationary support. The gaseous fluid emitted by the gas emanatingsurface of the stationary support possesses an associated gaseouspressure. Pressure is force per unit area and thus the gaseous pressureof the gaseous fluid emitting from the gas emanating surface of a fluidemanating stationary support can exert a force on an object upon whichsaid flow impinges. When a substrate is fluidically levitated using aporous gas emanating stationary support the total gaseous fluid flow iskept as low as possible and the constant gaseous fluid flow provides alocalized constant positive pressure region, that is—a localizedconstant force per units area, perpendicular to the substrate in such amanner as to oppose the force of gravity.

In the special case of a planar porous gas emitting surface, the gaseousfluid layer residing between the substrate surface opposed to the gasemitting surface and the gas emitting surface has a parabolic shapedpositive pressure profile in the space between the porous surface andthe opposing substrate or support surface. A positive pressure profileis a pressure profile where the pressure in the region of interest isgreater than the surrounding ambient gaseous pressure found at thecircumference of the substrate, said region of interest being the volumebetween the gas emanating surface of the stationary support and theopposing substrate surface that is occupied by the flowing gaseousfluid. If the integrated force produced by the positive pressure profileacross the substrate surface is sufficient to overcome the force ofgravity on the movable substrate the said integrated force results influidic levitation of the substrate. Thus, a positive pressure profileproducing an integrated force whose magnitude is larger than theopposing force of gravity is employed to provide sufficient force in theform of pneumatic pressure so as to overcome an opposing force such asgravity, thereby achieving pneumatic levitation. In the case oflevitation using a fluid emanating from a porous surface, the emanatingfluid exhibiting a positive pressure profile also has a laminar flowpattern whose streamline are directed towards the substratecircumference in the region between the porous surface and the substratesurface. This method of pneumatic levitation of a substrate on a gaseousfluid layer and the associated fluid hydrodynamics is described by J. S.Osinski, S. G. Hummel, and H. M. Cox in the article titled “VaporLevitation Epitaxy Reactor Hydrodynamics” (J. Electronic Materials,16(6), (1987), 397-403). In the method described by Osinski et al thepressure orthogonal and normal to the substrate surface, that is,perpendicular to the substrate surface, is balanced against the opposingforce of gravity, to provide the desired pneumatic levitation, (alsocalled gaseous flotation), of the moveable substrate. According toOsinski's description of vapor levitation hydrodynamics, the gaseouspressure in the volume between the movable substrate and the opposingsurfaces of the porous gas emitting surface is above ambient pressure atall points under the substrate—ambient pressure being defined as theprevailing gaseous pressure in the surrounding environment proximate tothe substrate and the stationary gas emitting support. Lateral movementof the substrate is still possible when the gas-emanating stationarysupport is comprised essentially of a porous gas emitting surface, andthe use of physical stops is advantageous to restrict lateral motion ofthe substrate during levitation as the restraining force of theorthogonal gas flow is not sufficient to impede lateral motion of thesubstrate. The substrate can move in manner similar to a hockey puck onice in the absence of physical stops the restrain lateral motion.

In a second embodiment or configuration, the pneumatic layer employed toproduce a gravity opposing pneumatic force required for pneumaticlevitation is provided by a stationary assembly or support having anon-porous surface through which fluid will flow with a defined surfacearea and providing a gas flow in such a way that the gas flow isdistributed across an area of the opposing face of the substrate using asupport with a non-porous surface through which fluid will flowcontaining at least one fluid collimating conduit, nozzle, bore ororifice in fluid communication with a pressurized manifold or plenum,thereby enabling pressurized fluid to flow through the fluid collimatingconduit, nozzle, bore, or orifice, resulting in the production of atleast one high velocity fluid flow emanating from the stationary supportsurface. The high-velocity fluid flow emanating from the fluidcollimating conduit, nozzle, bore, or orifice is also called a fluidjet. Unless described to the contrary, the term “fluid collimatingconduit” refers to a structure through which fluid flows and assistswith alignment of the stream lines of the fluid flow. It is understoodthat in practice it is difficult to achieve completely collimated oraligned fluid flow and fluid collimating conduits of the presentinvention include fluid collimating conduits that produce partiallycollimated fluid flows. Thus the non-porous surface of the gas-emanatingstationary support through which fluid will flow contains at least onefluid collimating conduit, nozzle, bore, or orifice in fluidcommunication with a pressurized manifold or plenum, thereby enablingpressurized fluid to flow through the fluid collimating conduit, nozzle,bore, or orifice, resulting in the production of at least one fluid jetimpinging on the opposing substrate surface. The opposing movablesubstrate surface facing the stationary gas emitting surface containingat least one fluid collimating conduit, nozzle, orifice, or bore followsthe contours of the stationary gas emitting surface in a conformal-likemanner. The surface area of the moveable substrate can be less than thatof the stationary support, equal to that of the stationary support, orexceed that of the stationary gas emitting support surface. For example,a web of a moveable substrate that is pneumatically levitated over agas-emanating stationary support supplying a frictionless, gravityopposing, thin layer of gaseous fluid between the web and the surface ofthe stationary support is an example of a moveable substrate whosesurface area is larger than the opposing gas-emanating stationarysupport. The amount of surface area of the moveable substrate and theamount of surface area of the gas-emanating stationary support relativeto the cross-sectional area of the gas emanating orifice is importantfor pneumatic levitation: the surface area of the stationary fluidemanating support is at least four times larger than both thecross-sectional area of the fluid collimating conduit, orifice, nozzle,or bore and the cross-sectional area of the collimated fluid jet flowingproduced by said fluid collimating conduit, orifice, nozzle, or bore forrobust fluidic levitation. Similarly, the surface area of the opposingsubstrate surface is at least four times larger than the cross-sectionalarea of the fluid collimating conduit, orifice, nozzle, or bore and thecross-sectional area of the collimated fluid jet produced by said fluidcollimating conduit, orifice, nozzle, or bore for robust fluidiclevitation.

In a third embodiment or configuration, the pneumatic layer employed toproduce a gravity opposing pneumatic force required for pneumaticlevitation can be provided by a stationary assembly or support throughwhich fluid will flow having a non-porous surface with a defined surfacearea and providing a gas flow in such a way that the gas flow isdistributed across an area of the opposing face of the substrate using asupport with a plurality of fluid collimating conduits, nozzles, bores,or orifices, usually arranged in a specific pattern, where the pluralityof fluid collimating conduits, nozzles, bores, or orifices is in fluidcommunication with a pressurized manifold or pressurized plenum, therebyenabling pressurized fluid to flow through the fluid collimatingconduits, bores, or orifices resulting in the production of a pluralityof gaseous fluid jets emanating from the stationary support surface. Theopposing movable substrate surface facing the stationary gas emittingsurface containing a plurality of fluid collimating conduits, maycontain only small features and is essentially conformal to thestationary gas emitting surface topography—that is, the shape of themoveable substrate surface essentially follows that of the gas emittingstationary support. As mentioned previously, the surface area of themoveable substrate can be less than that of the stationary support,equal to that of the stationary support, or exceed that of thestationary gas emitting support surface.

The fluid collimating conduits, nozzles, bores, or orifices in thefluid-emitting stationary support through which fluid will flow mayproduce gaseous jets of varying orientation relative to the stationarysupport surface normal. The gaseous jets can be parallel to thestationary gas emitting surface normal, in which case they are calledorthogonal jets or normal jets that emit from the stationary surface.Gaseous or liquid fluid jets that have their velocity vector parallel tothe surface normal are also called jets that are orthogonal or normal tothe reference surface, the reference surface being the surface of thestationary support. Alternatively, the stationary support may containfluid collimating conduits, nozzles and bores that are not orientedparallel to the stationary support surface normal and these fluidcollimating conduits can produce fluid jets that can be tilted at anangle relative to the surface normal as described by Yokajty in U.S.Pat. No. 5,470,420 (referenced above). Fluid jets where the fluid is agaseous or a liquid and whose velocity vector is not parallel to thestationary support normal are called non-orthogonal jets. Fluid jetswhere the fluid is a gaseous or a liquid and whose velocity vector innot parallel to the stationary support normal are also called tiltedjets because they are tilted with respect to the reference surfacenormal and are not parallel to the normal of the reference surface ofthe stationary support. When a plurality of fluid jets, comprised ofeither orthogonal jets, non-orthogonal jets or both orthogonal andnon-orthogonal jets, are used to achieve pneumatic levitation the totalgaseous fluid flow is often kept as low as possible.

When all jets are closely spaced orthogonal jets, the jets beingorthogonal with respect to the gas-emitting stationary support and themoveable substrate is oriented parallel to the stationary supportsurface, then all jets are orthogonal to the moveable substrate also. Inthis configuration the gaseous fluid flow provides a constant pressureperpendicular to the substrate by virtue of the interaction of the fluidflow from the closely space orthogonal jets and the flow patterns aresimilar to those found when the stationary support is a porous surface.This method of pneumatic levitation is similar to the well-known gasbearing, which may utilize fluid collimating conduits, nozzles, bores,or orifices or slots to accomplish the generation of a frictionlesspositive pressure gaseous film between two surfaces. In one embodimentof a gas bearing employing fluid collimating conduits, nozzles, bores,orifices as a way of providing positive gas pressure underneath asubstrate surface, pneumatic levitation of the moveable substrate is theresult of the gravity opposing force provided by the positive pressureof the gaseous fluid layer located between the moveable substrate andthe stationary support as it flows towards the edges of the movablesubstrate, there being no pressure below ambient produced anywhereunderneath the substrate surface during pneumatic levitation process.Gas bearings may also be formed with a variety of other fluid deliveryconfigurations, including the transverse flow configuration described byLevy et al in U.S. Pat. No. 8,398,770 B2. In the transverse flowconfiguration the gaseous fluid travels in and is essentially confinedto a pressurized channel. The gas emanating from one or more of thesepressurized channels can provide a pneumatic force perpendicular to thesurface of the moveable substrate and additionally opposing thegravitational force on the apparatus in which the pressurized channelsare contained, said pneumatic force being sufficient to allow pneumaticlevitation of the channel containing apparatus.

Pneumatic levitation can be accomplished using a single gaseous jet thatis orthogonal to locations on both the gas-emanating stationary supportand the opposing surface of a moveable substrate and the gas from thesingle gaseous jet is used to provide a frictionless gaseous cushion orgaseous layer upon which the non-stationary substrate can be supportedso that there is no physical contact between the substrate and thegas-emanating stationary support. Pneumatic levitation of this type thatis accomplished by using an orthogonal jet that is orthogonal to boththe stationary support and the opposing surface of a moveable substrateis known more generally as Bernoulli levitation, and is sometimes alsoreferred to as Bernoulli floatation, or Bernoulli airflow.

Unlike the “vapor levitation” described by Osinski et al, Bernoullilevitation with orthogonal jets relies upon the complex fluid mechanicbehavior of the gaseous fluid layer located between a gas emanatingsupport surface and an opposing substrate surface that is supplied by asingle orthogonal gaseous jet to produce a frictionless gaseous layerbetween the gaseous jet emitting surface and the opposing substratesurface. This is the same levitation method referred to in U.S. Pat. No.5,370,709. Fluid mechanic models describing and distinguishing Bernoullilevitation with gases from other methods of pneumatic levitation, suchas those forms of levitation employed in air bearings, have recentlyappeared in the open scientific literature—for example, see Waltham etal, (Waltham, C. E., Bendall, S., Lotlicki, A., “Bernoulli Levitation”,Am. J. Phys. 71 (2003) 176-179).

Without wishing to be bound by theory, computational fluid-mechanicalmodels have led to the assertion that in the case of Bernoullilevitation the two surfaces involved in levitation, meaning the twosurfaces that are orthogonal to the gaseous jet, each should have anarea that is at least 4 times larger than the cross-sectional area ofthe jet itself.

As the jet-to-jet distance and spacing between the nozzles or fluidcollimating conduits in the stationary support increases, the limitingcase of a single jet employed for pneumatic levitation is reached. Ofparticular interest in the present invention is the configuration whereonly a single fluid collimating conduit, nozzle, bore, or orifice iscontained in a non-porous stationary support through which fluid willflow and is in fluid communication with a pressurized manifold orpressurized plenum that is pressurized with a fluid, the fluid being agas; the single fluid collimating conduit generating a single orthogonalgaseous jet; the orthogonal gaseous jet impinging on an opposingsubstrate in an orthogonal manner; the surface area of the stationarysupport being at least 4 times larger than the cross-sectional area ofthe fluid emitting fluid collimating conduit; and the surface area ofthe opposing substrate surface being at least 4 times larger than thecross-sectional area of the fluid emitting fluid collimating conduit.

In one embodiment, the two surfaces involved in levitation, meaning thetwo surfaces that are orthogonal to the gaseous jet, each should have anarea that is at least 4 times larger than the cross-sectional area ofthe fluid emitting fluid collimating conduit, nozzle, bore, or orificecontained in the fluid emanating stationary support, said fluidcollimating conduit, nozzle, bore, or orifice being capable of producinga localized gaseous jet using gas flowing from a gas emitting supportsurface containing at least one of said fluid collimating conduit,nozzle, bore, or orifice; said fluid collimating conduit, nozzle, bore,or orifice being capable of producing a gaseous jet whose velocityvector is essentially orthogonal to at least one point on the gasemitting surface and whose velocity vector is additionally essentiallyorthogonal to at least one point on the opposing substrate surface.

Again without wishing to be bound by theory, it is believed that thedescription of Bernoulli air-flow levitation with orthogonal jetsinvolves complex fluid flow patterns: as the orthogonal jet interactswith the opposing surface the orthogonal jet strikes or impinges on thesurface of the opposing substrate. A stagnation point where there is nofluid movement is established proximate to the opposing surface and thedirection fluid flow of the jet changes proximate to the stagnationpoint at the opposing substrate surface in a manner that appears as ifthe stagnation point was deflecting fluid from contact with the surfaceat the stagnation point location. The flow pattern thereby establishedis sometimes called stagnation flow and occurs over a cross-sectionalarea defined by the jet impingement region on the opposing substratesurface said cross-sectional area being at least as large as the fluidjet cross-sectional area. The fluid flow proximate to the stagnationpoint rapidly changes direction, turning 90 degrees relative to theinitial jet velocity vector and becomes a radial symmetric flow centeredaround the impingement region of the orthogonal jet on the opposingsubstrate surface. When this directional reorientation of the flowoccurs there is an abrupt change in the direction of the fluid velocityvector from a velocity vector which is essentially orthogonal to thesubstrate surface to a velocity vector that is essentially parallel tothe opposing substrate surface. The velocity vector of the fluid flowundergoes a large change in magnitude as the fluid expands radiallyoutwards. The horizontal velocity component that is parallel to theopposing substrate is essentially zero at the edge of the gaseousorthogonal jet and when the jet changes direction as it flows around thestagnation point on the substrate surface the horizontal velocitycomponent increases substantially during radial expansion of the fluid.The sudden change in horizontal fluid velocity that occurs as the fluidexpands radially into the volume surrounding the orthogonal jet producesa radially symmetric localized region of reduced pressure surroundingthe jet, as described by Bernoulli's theorem. Bernoulli's equation andtheorem is well known to those skilled in the art of fluid mechanics. Asthe fluid further expands into the increasingly large annular volumesurrounding the orthogonal jet, the velocity of the gaseous fluidgradually decreases in a manner inversely proportional to distance fromthe jet until it reaches the circumference of either the levitatedsubstrate or the stationary gas emitting support (whichever is reachedfirst)—at which point the pressure of the gaseous fluid equalizes withlocal surrounding or ambient pressure, the local surrounding or ambientpressure being defined as the prevailing gaseous fluid pressureproximate to both the moveable substrate and the gas-emanatingstationary support. Conservation of mass dictates that the sum total ofthe flow over all exit points of the radial flow equals the total flowinjected into the volume between the moveable substrate and thestationary support by the orthogonal jet.

The spatial profile of gaseous pressure in the volume between thegas-emitting support from whence the orthogonal jet emanates and theopposing substrate surface is complex with multiple features and is adistinguishing feature of Bernoulli levitation and Bernoulli airflowwith condensed liquid fluids and gaseous fluids. During pneumaticBernoulli levitation there is a high pressure region where theorthogonal jet impinges on the opposing substrate and producesstagnation flow. The high-pressure region associated with impingement ofthe orthogonal jet on the opposing substrate surface generates a netforce which acts to push away the opposing surface of the moveablesubstrate from the gas-emanating stationary support. The localizedhigh-pressure region in the volume between the moveable substrate andthe stationary support is surrounded by a reduced pressure region thatextends radially outwards in a radially symmetric fashion. The minimumpressure found in the reduced pressure region is significantly lowerthan the stagnation pressure found at the jet impingement location onthe opposing substrate, and the reduced pressure rises to ambientpressure in a monotonic fashion outward along the symmetric radial flowdirection from the edge of the orthogonal jet to the ambient pressureexit point of the radial flow. The reduced-pressure region generates anattractive force between the moveable substrate and gas-emanatingstationary support, and thus the internal pneumatic pressure from theflowing gas in the radial flow region “pulls” the opposing substratesurface towards the stationary support. The complex spatial pressuredistributions produced in the volume between the moveable substrate andthe stationary support during pneumatic Bernoulli levitation arecharacterized by both attractive and repulsive forces that furtherinteract with the gravitation force on the moveable support to producepneumatic levitation when sufficient flow is present. The integratedforce on the surface of the moveable substrate is the sum of all theforces present and includes the force of gravity as well as thepneumatic forces produced by both the impinging high pressure orthogonaljet and the integrated force over the remaining substrate surface thatresults from the reduced pressure region, or low pressure region,surrounding the impinging orthogonal jet. There are, then, multipleforces produced by pneumatic flow from the orthogonal jet in the volumebetween the moveable substrate and the stationary support: theorthogonal jet produces a repulsive force that acts to push the moveablesubstrate away from the stationary support and the low pressure in theradial flow region produces a net attractive force that acts to pull themoveable substrate closer to the stationary support. The net forcegenerated when sufficient flow is present to produce pneumaticlevitation by overcoming the effect of gravitational force on asubstrate is referred to as “suction” in U.S. Pat. No. 5,370,709(referenced above).

Without wishing to be bound by theory, computational fluid-mechanicalmodels have led to the assertion that in the case of Bernoullilevitation the two surfaces involved in levitation, meaning the twosurfaces that are orthogonal to the gaseous jet, also leads to uniquedistributions of chemically reactive species during fluid flow. Duringpneumatic levitation of a moveable substrate using a single orthogonaljet emanating from a stationary support, the gas from the orthogonalimpinging jet expands radially into the surrounding volume. As the fluidexpands into cylindrical annuli of ever increasing radius, the volumeincrease of successive cylindrical annuli encountered as the fluid flowsradially outward is directly proportional to the distance from the jet.Thus, if a pulse or small quantity of material is injected into theorthogonal jet and produces a number density of ξ of molecules/unitvolume at the impingement location of jet, as these molecules flowradially outward and are diluted by additional flow the number densityof the molecules will vary as (ξ/r) where r is the radial distance fromthe impingement location of the orthogonal jet on the moveablesubstrate. In other words, the number density or concentration of themolecules in the volume between the stationary support and the moveablesubstrate will decrease in a manner inversely proportional to thedistance from the jet as the injected pulse flows radially outward. Atthe same time, both experimental measurements and theoreticalcalculations show that the velocity with which the molecules flowoutward falls off in a manner that is inversely proportional to r—whichmeans that the residence time of a molecule at a particular location isproportional to the distance from the jet. Thus, the product of theconcentration of molecules, (which is inversely proportional to r), andthe residence time, (which is proportional to r), is constant duringradial flow outward from the jet impingement location. The product ofconcentration or molecular number density and residence time is known asexposure, and is related to the amount of time that a surface is exposedto a given molecular flux. The radial outward flow from the orthogonallyimpinging jet has the unique property that exposure of a surface to avapor phase molecular species remains essentially constant as outwardradial flow proceeds as long as the consumption of the molecular speciesby secondary processes is small in comparison to the initial molecularnumber density. This unique property of radial flow configurations isparticularly advantageous for specific deposition processes involvingsurface adsorption like, for example, atomic layer deposition, or forany other process where uniform surface exposure is important to achievespatially uniformity of a chemical reagent on a substrate surface.

The velocities of the gaseous fluid phase as it undergoes outward radialexpansion can be quite large. Gas velocities approaching the speed ofsound are easily achievable and these high gas velocities lead to veryrapid gas exchange in the volume region defined by the gas emanatingsupport surface and the opposing surface of the moveable substrate.Depending on the pneumatic levitation height and fluid throughput,gaseous volume exchange as fast as 100 volume exchanges per second arepossible. The advantages of rapid gas volume exchange have beenpreviously disclosed in U.S. Pat. No. 5,370,709 with respect to vaporphase epitaxy processes where it is recognized that both particlecontamination and chemical contamination by volatile impurities areminimized in processes where rapid gas exchange is present. Processeshaving rapid gas exchange can also run faster, leading to higher processthroughput, especially if gas phase reactants or impurities must beremoved by a purge step while the process is running. The rapid gasexchange that is inherent to pneumatic levitation utilizing radial flowfrom a single orthogonal jet is particularly well suited for processeslike, for example, atomic layer deposition or vapor priming, wheregaseous reactants must be repeatedly swept away from the substratesurface during the process sequence.

As mentioned above, pneumatic levitation is the condition where theforce of gravity on a substrate has been equaled or exceeded by anexternal opposing force supplied by a fluid such as a gas or liquid.Pneumatic levitation is the result of a balancing of gravitational andpneumatic forces. The height to which a moveable substrate can belevitated is determined by a number of variables including moveablesubstrate mass, total pneumatic flow, and the configuration of thestationary gas emitting support and empirically is not highly variablewith respect to total pneumatic flow; however, a stationary gas emittingsupport with a single fluid collimating conduit producing an orthogonaljet and constant gas flow will produce variable height levitationdepending on the mass of the moveable substrate, the size of theorthogonal jet, and the volumetric flow of the orthogonal jet. Typicallevitation heights for pneumatic levitation for appropriately sizedorthogonal gaseous jets are less than 5 mm and often 0.5 mm or less, inother words, 500 microns or less.

In all of the pneumatic levitation methods previously described themoveable substrate is supported by a frictionless film of gas residingbetween the moveable substrate and the gas-emanating stationary support.The presence of unpredictable horizontal forces on the moveablesubstrate can result in undesirable substrate motion. For example, aslight tilt of the gas-emanating stationary support with a singleorthogonal jet or a failure to exactly center the centroid of themoveable substrate over the orthogonal jet can generate unbalancedpneumatic forces which lead to horizontal, lateral motion of themoveable substrate and eventually result in displacement of the moveablesubstrate from its initial position until the substrate is no longerpneumatically levitated. When pneumatic levitation fails, the moveablesubstrate collides with the gas-emanating stationary support. Particlegeneration as a result of the collision as well as the generation ofsurface defects due to the physical contact of the collision leads toincreased defectivity on the moveable substrate surface. Irregularitiesin gas flow patterns as a result of excessive surface roughness on thesurface of the gas-emanating stationary support or the surface of theopposing substrate can produce similar results. U.S. Pat. No. 3,466,079notes that during pneumatic levitation with an orthogonal jet it is“nearly impossible to center the exit orifice for the pressurized fluidover the support . . . . As a result, there is a force component tendingto laterally shift the slice relative to the reference surface”. Thus,the art clearly discloses the difficulty associated with implementingpneumatic levitation methods and keeping the moveable substratestationary during processing of any type. Prior art has attempted toaddress this problem through the use of physical restraints such asedges and stops that provide physical contact with the moveablesubstrate edges and minimize undesirable motion. For applications suchas the label positioning application described by Yokajty in U.S. Pat.No. 5,470,420 (referenced above) such a solution is acceptable; however,any physical contact to a substrate can result in substrate defects.Some substrate defects due to physical contact between the substrate andthe stationary support during pneumatic levitation include edgedeformation due to physical damage of the edge from physical contactwith the stops, particle generation on the substrate surface, chippingof edges of brittle moveable substrates, and abrasion leading toparticle formation and substrate deformation. In many applicationsinvolving the manufacture of high-value products with brittle or rigidsubstrates such as semiconductor integrated circuits, electro-opticalcomponents, and optical films particle related and deformation relateddefects must be minimized.

Levitation Stabilizing Structure

It has now been discovered that the problem of positional stability ofthe moveable substrate during pneumatic levitation with radiallysymmetric flow fields—including the radially symmetric flow fieldsproduced by the annular nozzles arrays described in U.S. Pat. Nos.5,492,566 and 5,967,578 (referenced above) can be addressed through theuse of a levitation stabilizing structure fabricated on the moveablesubstrate itself rather than through the use of guides or restrainingdevices located on the gas-emanating stationary support as has beendescribed in the prior art. Furthermore, it has been found that thefabrication of a levitation stabilizing structure for the purpose ofprocessing the moveable substrate by employing pneumatic levitation andthe subsequent removal of said levitation stabilizing structure afterthe processing step is compatible with the normal workflow encounteredin the manufacture of integrated circuits, electrical components, andoptical films.

Referring to FIG. 3 in an embodiment of the present invention, amoveable substrate 10 has a levitation stabilizing structure 30 (LSS)located on a surface of the moveable substrate 10 and enclosing an areaof the moveable substrate 10. The enclosed area forms an interiorimpingement area 35. The moveable substrate 10 is comprised of at leastone material layer. The moveable substrate 10 can have existing layersor thin films contacting and overlaying the surface of at least onematerial layer of moveable substrate 10. In one embodiment, one or moreatomic thin-film layers 50 are formed on the moveable substrate 10 inthe interior impingement area 35. The levitation stabilizing structure30 extends away from a surface of the moveable substrate 10 and can haveinterior walls 38 that are perpendicular (shown with perpendicular 32)to the moveable substrate 10 surface. The levitation stabilizingstructure 30 has a levitation stabilizing structure surface 36 incontact with the moveable substrate 10 surface and a top surface 34 on aside of the levitation stabilizing structure 30 opposed to the moveablesubstrate 10.

In one embodiment of the present invention, the moveable substrate 10 isplanar. In another embodiment, the moveable substrate 10 is not planar,and, for example the moveable substrate 10 is spherical, is a section ofa sphere, or has a topography like a structured surface. As used herein,a structured surface is one in which portions of the surface extend awayfrom the moveable substrate 10. In one embodiment, the structuredsurface can have the portions of the surface extending away from themoveable substrate similar in size to features associated withintegrated circuits. Thus, the structured surface on moveable substrate10 can be comprised of at least one integrated circuit. The structuredsurface of moveable substrate 10 can be comprised of at least onemicrofluidic device. The structured surface of moveable substrate 10 canbe comprised of at least one electro-optical device. The structuredsurface of moveable substrate 10 can be comprised of at least onemicroelectromechanical system. The structured surface of moveablesubstrate 10 can be comprised of at least one micromachine. Thestructured surface of moveable substrate 10 can be comprised of at leastone molecular electronics circuit. The structured surface of moveablesubstrate 10 can be comprised of at least one micro-optical assemblies.The structured surface of moveable substrate 10 can be comprised of atleast one interconnect assembly. As used here, an interconnect assemblyprovides communication between locations, the medium of communicationbeing electrical, fluidic, optical, acoustic, radiative, or any othermedium used for provide continuity between two locations. In oneembodiment, the structured surface of moveable substrate 10 can becomprised of at least one electrical interconnection assembly. Inanother embodiment, the structured surface of moveable substrate 10 canbe comprised of at least one microfluidic device interconnect assembly.

FIG. 3 is a cross-sectional view of levitation stabilizing structure 30fabricated on a plate-like moveable substrate 10. The drawing in FIG. 3is not drawn to scale: the size relationship between moveable substrate10 and levitation stabilizing structure illustrated in FIG. 3 is notexact and has been altered in order to better illustrate the inventionand method of use. Although moveable substrate 10 is shown as havingparallel planar surfaces, moveable substrate 10 is not bound by thisrestriction. The surfaces of moveable substrate 10 can betopographically complex. For example, the surface of moveable substrate10 can be spherical in shape and form with other additionaltopographical features. The levitation stabilizing structure 30 is athree-dimensional structure and has at least one surface 36 contactingand overlaying a surface of moveable substrate 10; at least one interiorwall 38; at least one surface 34 at a height above the surface ofmoveable substrate 10 wherein the height of surface 34 above the surfaceof moveable substrate 10 is the thickness of at least one material layerand the thickness is essentially defined by the length of a line segmentidentified by perpendicular 32 that resides between two points one ofwhich contacts surface 34 and the other of which contacts the surface ofmoveable substrate 10, said line segment being normal to both surfaces.It is desirable that perpendicular 32 be parallel to the interior wall38 of levitation stabilizing structure 30 as shown in FIG. 3 but it isnot required that the interior wall feature 38 of levitation stabilizingstructure 30 extending between surface 34 with the surface of moveablesubstrate 10 exhibit strict parallelism with perpendicular 32 at eachlocation. Practical experience with fabrication of the levitationstabilizing structure suggests that the interior wall 38 can deviatewith respect to parallelism with perpendicular 32 whilst retaining thefunctionality of the levitation stabilizing structure for positionalstabilization during fluidic levitation. The interior impingement area35 of the levitation stabilizing structure is the region of the surfaceof moveable substrate 10 that is surrounded and enclosed by the interiorwalls 38 of levitation stabilizing structure 30 in a continuous mannersuch that the levitation stabilizing structure functions as aconfinement area that restricts direct communication of the surface areaof interior impingement area with the surrounding surface area ofmoveable substrate 10 that is outside of the levitation stabilizingstructure 30.

In one embodiment of the present invention, the levitation stabilizingstructure 30 has a rim enclosing the interior impingement area. The rimcan have a height above the moveable substrate 10 that is less than orequal to 5 mm and greater than or equal to 50 microns. Alternatively,the rim has a height above the moveable substrate that is less than ⅔ ofthe distance between the moveable substrate 10 and the stationarysupport 12.

An atomic thin-film layer is a material layer comprised of one or moreatomic layers on a surface. One or more atomic layers can be formed onthe surface of the interior impingement area 35 on moveable substrate 10by exposure of the surface to at least one molecular flux. The surfaceof the interior impingement area 35 is full of atomic scale features andimperfections called surface sites, some of which are non-chemicallyreactive and others of which are chemically reactive. The total numberof surface sites on a surface is characterized by a measurement of howmany molecules can sit on the surface in a single layer. The number ofmolecules sitting on a surface in a single layer is known as a monolayeror atomic layer and is typically around 10¹⁵ molecules/cm². There can bemore or less adsorbed molecules in an atomic layer depending on thenature of the surface (material and crystallographic orientation), thetemperature of the surface, the type of molecule being investigated, thepartial pressure of said molecules, and the exposure time of the surfaceto the partial pressure of said molecules. An atomic layer of moleculesis formed on a surface when molecular species attach themselves to asurface either by physical adsorption or by chemisorption. Physicaladsorption relies on Van der Waals attraction to maintain attractionbetween the adsorbed molecular species and the surface. Chemisorptionrelies on the formation of a chemical bond between the molecular speciesand the surface to maintain attraction between the adsorbed molecularspecies and the surface. The formation of atomic layers by chemisorptionis preferred for atomic layer deposition processes. Atomic layersoverlaying and in contact with one another can be formed when a surfaceis sequentially exposed to two different molecular fluxes whosemonolayers or atomic layers chemisorb on each other. For example,molecule A may form an atomic layer on a surface and then molecule B mayform a molecular layer by chemisorption onto the pre-existing atomiclayer of molecule A. Furthermore, molecule A may form an additionalmolecular layer by chemisorption onto the pre-existing layer of moleculeB, and so on. In this manner multiple atomic layers can be formed on asurface through the use of sequential chemisorption processes. Thepresent invention is useful for efficiently and rapidly forming one ormore atomic thin-film layers on a moveable substrate. In a furtherembodiment the atomic thin-film layers are patterned. Moreover, atomicthin-film layers are typically conformal, so that a structured surfaceon the moveable substrate 10 is coated to a consistent thickness.

In one embodiment the levitation stabilizing structure is comprised of amaterial layer having one side in contact with a substrate; having athickness greater than 20 microns; wherein part of the material layer ofthe levitation stabilizing structure is absent so as to expose thesubstrate surface, said substrate surface often being exposed for thepurpose of exposure to subsequent processing; and the exposed area ofthe substrate, when viewed normal to the exposed substrate surface,having the shape of a convex or concave polygon whose centroid islocated within the area enclosed by the polygon; wherein the area of theexposed surface within the polygon is at least 4 times larger than thecross-sectional area of the impinging collimated fluid jet employedduring the fluid levitation process.

The material layer of the levitation stabilizing structure (LSS) can beprovided by forming or fabricating the LSS using additive processes. Forexample, deposition processes can be employed to form a levitationstabilizing structure material layer having properties appropriate forthe substrate type and the levitation application. The LSS can becomprised of multiple layers. The LSS can comprise a material layer andan adhesion promoting layer to enable secure attachment of the LSS tothe underlying substrate. Alternately, the LSS can be provided usingsubtractive forming processes to form a material layer having propertiesthat are appropriate for the substrate type and the levitationapplication. Furthermore, the LSS can be formed using both additive andsubtractive processes, as is the case when a photoresist is applied to asubstrate and patterned and cured in an imagewise manner so that some ofthe photoresist layer is removed in order to form a levitationstabilizing structure.

A method or means for providing a levitation stabilizing structure on asubstrate is to print the levitation stabilizing structure directly onthe substrate using a 3 dimensional printing technology. Such a methodof providing a levitation stabilizing structure on a substrate can beextremely rapid, clean, and convenient. In another embodiment thelevitation stabilizing structure on a substrate is printed directly onthe substrate using a screen printing method.

Another embodiment of providing a levitation stabilizing structure on asubstrate is through the use of material layer that is patternable. Amethod for providing a levitation stabilizing structure through the useof patternable layers includes the following steps in order:

providing a substrate;

adding a patternable material layer to at least one surface of thesubstrate so that the patternable material layer is in contact andoverlaying with at least one surface of the substrate;

patterning the patternable material layer in an imagewise manner; and

forming a levitation stabilizing structure from the patterned materiallayer, said levitation stabilizing structure comprised of a materiallayer with a depressed polygonal shaped feature, said levitationstabilizing structure overlaying and in contact with at least onesurface of the substrate.

The patternable layer can be patterned by any means known in the art.Means for producing patterns on patternable layers include, for example,imprinting, embossing, hydroforming, sandblasting through a mask,selective chemical and plasma etching, photopatterning withphotosensitive materials. The patternable layer can be a photoimageablematerial layer. The patternable layer employed to prepare the levitationstabilizing structure can be a curable material with cross-linkingagents. The patternable layer can be a photosensitive material layer.Examples of a photoimageable material layers are positive and negativephotoresists, including dry film photoresists which are laminated uponthe surface of the substrate in a conformal-wise manner. The LSS can becomprised of multiple layers wherein one of the layer is an adhesionpromoting layer. The adhesion promoting layer element of the levitationstabilizing structure can be added on the substrate surface upon whichthe patternable material layer overlays to improve the robustness of thefabricated LSS. It is recognized that the patternable material layer instep b) of the method for providing an LSS using patternable layersabove does not have to be at least 20 microns thick: a patternable layermay have a thickness less than 20 microns if the patterning processutilizing the patternable layer can be employed as an essential means,for example—as a template—to produces thicker layers. An example of athin patternable layer that provides and essential means to produce athicker patterned material layer is a thin evaporated metal layer thatis patterned and electroplated to produce a levitation stabilizingstructure have a thickness 20 microns or greater. Electroless depositionof thick material layers on a patterned catalytic seed layer is anotherexample of a thin patternable layer that provides an essential means toproduce a thicker patterned material layer.

Alternatively, the LSS can be fabricated externally then applied to thedesired surface of the substrate. The externally fabricated LSS can becomprised of multiple layers. In one embodiment, a levitationstabilizing structure is comprised of a material layer and an adhesivelayer. In another embodiment a levitation stabilizing structure iscomprised of a material layer and an adhesion promoting layer. The LSScan be applied to the desired surface of the substrate using any meansknown in the art including lamination, pressing, sintering, heating,gluing, or other methods familiar to those skilled in the art ofmechanical assembly.

Thus, an alternate method for forming a levitation stabilizing structureon a substrate is comprised of the following steps in order:

providing a levitation stabilizing structure comprised of a materiallayer having a thickness greater than 20 microns; wherein part of thematerial layer of the levitation stabilizing structure is patterned andthe patterned area of the material layer, when viewed normal to theplane of the material layer, has the shape of a convex or concavepolygon whose centroid is located within the area enclosed by thepolygon;

providing a substrate; and

adhering the levitation stabilizing structure to the substrate in aconformal-wise manner so that the levitation stabilizing structureoverlays and is in contact with the substrate surface in aconformal-wise manner and the substrate surface is exposed where thematerial layer of the levitation stabilizing structure is absent; andthe exposed area of the substrate, when viewed normal to the exposedsubstrate surface, has the shape of a convex or concave polygon whosecentroid is located within the area enclosed by the polygon.

An example of a levitation stabilizing structure that can be employedfor the method above is a levitation stabilizing structure that isfabricated in the form of a label with an adhesive layer where theadhesive layer is protected by a protective cover tape. The label is cutwith a pattern reflecting the shape of the desired polygonal levitationstabilizing structure. For example, the desired levitation stabilizingstructure can be shaped like an annulus so the levitation stabilizingstructure is formed as a label that is cut into the shape of an annulusof the appropriate dimensions. The cover tape protecting the labeladhesive is removed in the patterned region reflecting the desiredpolygonal levitation stabilizing structure to expose the label adhesiveand the levitation stabilizing structure is affixed to a surface of thesubstrate so that the levitation stabilizing structure is overlaying andin contact with the substrate surface in a conformal-wise manner, alladditional material of the label except for the annular levitationstabilizing structure being removed from the substrate surface. As usedherein the term “on” means “overlaying and in contact with”.

Alternately, the levitation stabilizing structure with can be fabricatedon an intermediate substrate by other methods such as 3 dimensionalprinting then transferred to the surface of the substrate and adhered tothe substrate surface using for example, an adhesive layer or usingheat. The precautions that are necessary to adhere a material layer to asubstrate in a conformal-wise manner are familiar to those skilled inthe art of lamination and mechanical assembly and include elimination ofbubbles and other defects that indicate lack of contact between thesubstrate and the overlying material layer. Without wishing to be boundby theory, it is preferred that the contours of the LSS closely followthe contours of the underlying substrate upon which it is mounted. Theformation of bubbles, ridges, and other surface non-uniformities andsurface imperfections in the LSS is undesirable because surfacenon-uniformities affect the characteristics of fluid flows over the LSSduring the fluidic levitation process.

In another embodiment the LSS can be fabricated as an integral part ofthe substrate itself by employing known technologies used to fabricatearticles of complex shape. Examples of technologies employed tofabricate articles of complex shape are conventional machiningprocesses, injection molding, extrusion, stamping, hydroforming,electroforming, 3 dimensional printing, and the like. The LSS may thusbe formed as a singular piece optionally integrated with the substratefor subsequent processing applications. In some configurations the areaof the LSS can be backfilled with an additional thin material layerresulting in a complex multilayer structure. The LSS can be formed froma wide variety of materials, and the subsequent use of the LSS is partof the criteria determining whether it is compatible with the underlyingsubstrate. The LSS can be comprised of multiple layers. The LSS can befabricated from the same material as the substrate, including materialof the substrate itself, or it can be fabricated from a material ofdifferent chemical composition. The levitation stabilizing structure canbe comprised of a material layer and one or more adhesion promotinglayers to facilitate the adhesion of the LSS to the underlyingsubstrate. In the aforementioned levitation stabilizing structureembodiments, the adhesion promoting layer or adhesive layer contributesto the overall height of the levitation stabilizing structure and isconsidered part of the levitation stabilizing structure. In oneembodiment, wafer bonding can be used to bond an ultrathin wafer to aLSS made from the same material so that the ultrathin wafer can beprocessed in a non-contact levitated manner.

In another implementation of the levitation stabilizing structure, amultilayer LSS can be formed directly using photoresist whose adhesionto the underlying substrate is optionally promoted by the use of, forexample, a vapor priming adhesion promoting layer likehexamethyldisiloxane (HMDS), employing either liquid or dry filmpositive or negative photoresist to form a patternable material layer onthe surface of the moveable substrate and patterning the photoimageablephotoresist material layer in an imagewise manner to form a convex orconcave polygon of appropriate area to enable either pneumatic orhydraulic levitation of the underlying substrate when the surface of thesubstrate upon which the LSS is fabricated is exposed to a suitablefluid flow. In this implementation, the fabrication of the levitationstabilizing structure takes advantage of fabrication methods normallyemployed in integrated circuit manufacture and is easily implemented inthe semiconductor integrated circuit fabrication workflow.

FIG. 4 is a cross-sectional view illustrating one embodiment of thepresent inventive method for practicing pneumatic levitation. FIG. 4shows a chamber 60 containing a moveable substrate 10 with a levitationstabilizing structure 30 fabricated thereupon. The surface of moveablesubstrate 10 with the levitation stabilizing structure 30 opposes thegas-emanating surface of stationary support 12. The stationary supportthrough which fluid will flow 12 is located in the chamber 60 forsupporting the moveable substrate 10. The stationary support 12 extendsbeyond the enclosed interior impingement area. The stationary support 12through which fluid will flow has a fluid collimating conduit 14positioned to deliver gas within the enclosed interior impingement area35 of the moveable substrate 10. A pressurized-gas source provides a gasflow through the fluid collimating conduit 14 impinging on the moveablesubstrate surface within the enclosed interior impingement area 35 ofthe moveable substrate 10 sufficient to levitate the moveable substrate10 and expose the moveable substrate 10 to the gas while restricting thelateral motion of the moveable substrate 10 with the levitationstabilizing structure 30. In one embodiment, the stationary support 12is located beneath the moveable substrate 10; in another embodiment, thestationary support 12 is located above the moveable substrate 10.

Fluid collimating conduit 14 is in fluid communication with apressurized fluidic source. In one embodiment, fluid collimating conduit14 is in fluid communication with a pressurized-gas source. In oneembodiment, fluid collimating conduit 14 is in fluid communication witha pressurized-liquid source. The cross-sectional shape of fluidcollimating conduit 14 can be varied with the provision that acollimated fluid jet can be formed at the exit side of the fluidcollimating conduit when pressurized fluid is applied to the entranceside of the fluid collimating conduit. The exit side of the fluidcollimating conduit is the side of the fluid collimating conduit opposedand facing the moveable substrate in FIG. 4. For example, thecross-sectional shape of fluid collimating conduit 14 can be arbitrarywith the provision that a hollow region exists for gas to flow through.Fluid collimating conduit 14 for producing a fluidic jet can have across-sectional shape of a simple polygon, convex or concave, with nvertices, where n≥3. Oval, elliptical and circular shapes are consideredpolygons with an infinitely large number of vertices and sides and thusare permissible for use in the construction fluid collimating conduit14. In one embodiment fluid collimating conduit 14 has a cylindricalshape open at both ends with a circular cross-section and provides fluidcommunication of opposing sides of stationary support 12 through whichfluid will flow. In another embodiment fluid collimating conduit 14 hasa cylindrical shape open at both ends with a circular cross-section andprovides fluid communication of opposing sides of stationary support 12and has additional helical shaped threaded grooves on the interiorsurface of the fluid collimating conduit to provide a rotational motioncomponent to the fluidic flow as it passes through fluid collimatingconduit 14. Helical grooves forming a thread like feature on theinterior surface of fluid collimating conduit 14 can impart rotationalmotion to a jet flow and thereby provide rotational motion to alevitating moveable substrate through centripetal force supplied by therotation of the fluid jet during contact with the moveable substrateduring fluidic levitation. FIG. 4 illustrates the appropriate relativepositions of the elements moveable substrate 10 with levitationstabilizing structure 30 relative to the stationary support 12 and fluidcollimating conduit 14 for the use of levitation stabilizing structure30 to be effective as a method of positional stabilization duringfluidic levitation with an orthogonal jet emanating from fluidcollimating conduit 14. It has been found that the use of the levitationstabilizing structure as a method for improving the lateral stability ofa moveable substrate during pneumatic levitation only requires that thefluid jet from jet forming fluid collimating conduit 14 of stationarysupport 12 impinges on the surface of moveable substrate 10 within theinterior impingement area 35 defined by the interior walls 38 of thelevitation stabilizing structure 30 fabricated on the surface ofmoveable substrate 10. It is preferred that the fluid jet from jetforming fluid collimating conduit 14 of stationary support 12 impinge onthe surface of moveable substrate 10 at or near the centroid of interiorimpingement area 35 defined by the interior walls of the levitationstabilizing structure 30 fabricated on the surface of moveable substrate10. Alternatively, the fluid jet from jet forming fluid collimatingconduit 14 of stationary support 12 impinges on the surface of moveablesubstrate 10 at or near the centroid of the moveable substrate 10. Thefluid collimating conduit on the stationary fluid emitting support is analignment feature on the surface of the stationary fluid emanatingsupport and the centroid of the interior impingement area of thelevitation stabilizing structure is aligned with the alignment featurewherein the alignment feature is a fluid collimating conduit on thesurface of the stationary fluid emanating support. Thus, the methodinventive for fluidic levitation includes the steps of:

providing a substrate;

fabricating a levitation stabilizing structure on a surface of asubstrate;

positioning the substrate proximate to a fluid emitting surface of astationary fluid emanating support in a conformal-wise manner with thelevitation stabilizing structure overlaying the surface of the substrateand facing the stationary fluid emanating surface through which fluidwill flow;

aligning the centroid of the interior impingement area of the levitationstabilizing structure with at least one alignment feature on the surfaceof the stationary fluid emanating support through which fluid will flow;

initiating at least one collimated fluid flow from the stationary fluidemanating support surface through which fluid will flow to produce acollimated fluid jet, and

controlling the collimated fluid flow emanating from the stationaryfluid emanating support to fluidically levitate the substrate andlevitation stabilizing structure proximate to the surface of thestationary fluid emanating support.

It has been observed experimentally that the alignment of the centroidof the interior impingement area of the levitation stabilizing structurewith at least one alignment feature on the surface of the stationaryfluid emanating support is not critical as the levitation stabilizingstructure exhibits self-alignment during the levitation process. Thereasons for self-aligning behavior during pneumatic levitation aredescribed in more detail below. This is a distinct advantage of using alevitation stabilizing structure during pneumatic levitation.

Mechanisms for accurately controlling the composition, temperature,pressure, and flow of the fluid that is employed for the purpose ofproducing a collimated fluid jet are known. Typical mechanisms forcontrolling pressure of gaseous fluids include both passively andactively controlled pressure regulators including electronicallycontrolled pressure regulators and other types of pressure regulatormethods known in the art. Typical mechanisms for controlling thetemperature of a fluid include feedback loops that control passive andactively controlled heating and cooling units including heat exchangers,feedback loops that control heating tapes and coils as well as coolingcoils through which the fluid passes, feedback loops that controltemperature controlled reservoirs, and feedback loops that control otherdevices known to those skilled in the art of temperature control offluids. Temperature and pressure control loops employed to achievestable fluid temperatures and fluid pressures may incorporate the useautomated temperature and pressure control units. Typical means andmechanisms for controlling the flow of one or more gaseous fluidsinclude the use of high-precision pressure regulators in conjunctionwith orifices of known diameter with known pressure-flow relationships,gas flow meters, flow controllers, control valves, and variable controlvalves of all types including mass flow meters and mass flowcontrollers, rotameters, Coriolis flow meters and flow controllers,turbine flow meters, pitot based flow meters and other types of fluidflow meters familiar to those skilled in the art of process control offlowing fluid media where the fluid is a liquid or a gas.

It is further recognized that the entire assembly represented by thecross-sectional view of FIG. 4 could be rotated by 180 around an axisnormal to the plane of FIG. 4 and the positional configuration willstill be functional. The use of a levitation stabilizing structure 30during fluidic levitation does not alter the function of a fluidiclevitation apparatus employing Bernoulli airflow with respect tophysical orientation of the apparatus, and in fact improves therobustness of fluidic levitation with respect to tilting of thegas-emanating stationary support regardless of the apparatus attitudeand orientation. Fluidic levitation can take place when the velocityvector of the orthogonal fluid jet is essentially parallel to thegravitational force vector or when the velocity vector of the orthogonalfluid jet is essentially anti-parallel to the gravitational forcevector. The presence of a levitation stabilizing structure 30 on themoveable substrate surface does not alter the relationships between thepneumatic forces that are generated by the fluid flow from theorthogonal jet that flows between the substrate surface and the fluidemitting support surface and the gravitational force vector that areinherently present in fluidic levitation processes employing Bernoulliairflow. This is a distinct advantage of the invention.

It is recognized that the stationary support 12 through which fluid willflow is not restricted to a planar configuration as illustrated in FIG.4. In one embodiment the features of the stationary support comprise thefollowing: the stationary fluid emitting support through which fluidwill flow contains at least one fluid collimating conduit in fluidcommunication with a manifold and a pressurized fluid source, said fluidcollimating conduit having a cross-sectional area less than or equal to¼ of the surface area of the interior impingement area of the levitationstabilizing structure; the surface area of the stationary fluid emittingsupport is at least equal to the surface area of the interiorimpingement area on the moveable substrate; and the fluid flow betweenthe stationary support and the moveable substrate is characterized byradial flow patterns that are essentially symmetric with respect to thecentroid of the interior impingement area. It is preferred that saidfluid collimating conduit have a cross-sectional area less than or equalto ¼ of the impingement area of the levitation stabilizing structure.

Thus, in one embodiment, if the moveable substrate 10 surface followsthe shape of an arc, as is found, for example, on the surface of anoptical lens, then a stationary support surface through which fluid willflow can be fabricated that follows the surface features of the moveablesubstrate surface and produces a radial flow pattern when an orthogonaljet impinges on the moveable substrate surface. Thus, the stationarysupport is fabricated to follow the surface features of the moveablesubstrate surface in a conformal-wise manner. In another embodiment, thestationary support topography opposing the moveable substrate resemblesa mold of the surface of the moveable substrate. In another embodiment,the stationary support topography opposing the moveable substratefollows the negative three dimensional image of the surface of themoveable substrate. In one example embodiment, the surface shape andform of moveable substrate 30 is continuous and smooth, monotonicallyvarying without a significant number of large surface protrusions;however, practical experience has shown that structured surfaces andsurface topographies having a height less than or equal to thelevitation stabilizing structure are well tolerated by fluidiclevitation processes. In other example embodiments, the surfacetopography of the moveable substrate 10 includes non-planar or includesthree dimensional structures that form a structured surface, forexample, surface portions that extend away from a base material layer ofthe moveable substrate 10.

The function of the levitation stabilizing structure fabricated on themoveable substrate surface is to harness the inherent kinetic energy ofthe gaseous flow of the fluidic layer employed in fluidic levitation soas to convert said kinetic energy into directional forces for thepurpose of introducing positionally restorative forces that act in arestorative manner to control and minimize undesirable lateral movementof the moveable substrate during fluidic levitation. The LSS is usefulwhen the fluid used for fluidic levitation is a gas or a liquid.

The symmetric radially outward flow which occurs during pneumaticlevitation processes employing one or more orthogonal jets can thus beharnessed to achieve positional stability of a pneumatically levitatedmoveable substrate using a levitation stabilizing structure fabricatedon the opposing surface of the moveable substrate. Furthermore, thefluid flow from one or a plurality of orthogonal or tilted jets containssubstantial pneumatic energy in the form of both kinetic and potentialenergy and this unharnessed pneumatic energy can be used to achievepositional stability of a pneumatically levitated moveable substrate.

Positional stability of the moveable substrate during pneumaticlevitation is achieved most readily when the stationary gas emittingsupport contains fluid collimating conduits, nozzles, bores, orifices,and fluid collimating conduits used for the generation of gaseousjets—tilted or orthogonal—that impinge within the interior impingementarea 35 on the surface of the opposing moveable substrate that is withinthe confines of the area defined by the interior walls 38 of thelevitation stabilizing structure that is located on and in contact withthe moveable substrate surface that opposes and faces the stationary gasemitting support surface, as shown in FIG. 3 and FIG. 4. The location ofthe levitation stabilizing structure on the moveable substrate is afeature that distinguishes the inventive method from all other previousattempts to address positional stability during pneumatic levitation.Furthermore, the inventive method is not restricted to planar plate-likesubstrates although planar substrates are preferred.

In one embodiment, the levitation stabilizing structure is a symmetricalstructure possessing a rotational axis of symmetry that is normal to theplane of the levitation stabilizing structure. The cross-sectional viewshown in FIG. 4 shows a dotted line indicating the position of theproper rotation axis of symmetry 40 of levitation stabilizing structure30 fabricated upon moveable substrate 10. A proper axis of rotation isnormally specified by the order of the axis, n. The proper rotation axisof symmetry has the property that an object rotated around the axis by360/n degrees is indistinguishable from the object in its original,unrotated position. For example, an axis centered in a square that isnormal to a plane containing the square has the property that it is anaxis of proper rotation of order 4. Thus, when the square is rotated360/4 or 90 degrees any direction around the axis it will appear as ifthe orientation of the square has not changed. Similarly, a circle has aproper rotation axis of order ∞ because an infinitely small amount ofrotation in any direction will generate an identical object to theoriginal circle. For the purposes of this inventive method, circles andovals are considered to be convex polygons because these two figures canbe considered to be formed from an infinitely large number of sides ofinfinitely small length and for this reason are considered convexpolyhedra having n vertices where n=∞. Another embodiment of thelevitation stabilizing structure is characterized by a levitationstabilizing structure possessing at least one symmetry element comprisedof a proper rotation axis wherein the proper rotational axis possessesan order that is two or greater.

Without wishing to be bound by theory, the means by which the levitationstabilizing structure functions will now be described for theconfiguration of a stationary gas emitting support through which fluidwill flow emitting a single orthogonal jet emanating from the stationarysupport surface impinging orthogonally on the opposing moveablesubstrate surface. It is found that the radial outward gas flow that isparallel to the moveable substrate surface can be harnessed to producerestorative forces using gas impingement on a barrier structuresuperimposed upon the moveable substrate surface and extending towardsthe stationary gas emitting support. The levitation stabilizingstructure is a barrier structure superimposed on the moveable substratesurface. The polyhedral shape of the barrier structure, said barrierstructure being the levitation stabilizing structure, influences thedirectionality of the restorative forces thereby produced by gasimpingement on the barrier structure. A barrier structure characterizedby a high degree of symmetry produces a set of highly symmetricrestorative forces. In one embodiment, the barrier structure iscomprised of a convex or concave polygon having at least w number ofsides where w≥3—that is, the polygon has at least three sides. Convexmeans that a straight line segment drawn between any two points locatedon any two distinguishable sides of the polygon does not intersect thecircumference of the polygon at any location except the two end pointsof said line segment. In another embodiment, the barrier structure has apolygonal shape with a proper rotation axis of symmetry of order n, alsocalled C_(n) that is orthogonal to the moveable substrate surface and tothe plane containing the symmetric barrier structure wherein n isgreater than or equal to 2. A convex polygon of the symmetric barrierstructure preferably has at least three sides in order to achieve abalance of horizontal pneumatic restorative force. The horizontalpneumatic restorative force is provided by sum of the each pneumaticforce produced by gas impingement pushing on the wall of the barrierstructure, said pneumatic force being parallel to the moveable substratesurface and produced by the sum of the pneumatic forces normal to thesides of the symmetrical convex polygon pneumatic barrier structure. Thehorizontal restorative force resulting from the sum of the pneumaticforces impinging normal to the walls of the symmetrical barrierstructure of the levitation stabilizing structure when the number ofwalls of the barrier structure w meet the condition w≥3 provides a fieldof balanced restorative forces that require the moveable substrate tocome to an equilibrium position and remain roughly stationary. Withoutwishing to be bound by theory, it is believed that when the centroid ofthe levitation stabilizing structure coincides with the mass centroid ofthe substrate then the equilibrium position for pneumatic levitation fora moveable substrate with a levitation stabilizing structure is theposition where the orthogonal jet impinges near the centroid of thepolygon shaped barrier structure. The centroid of a polygon is definedas the arithmetic mean of all the points in the polygon shape. Forexample, if a planar polygon is mapped onto a plane and each point onthe perimeter is designated an (x, y) coordinate value, then thecentroid of the planar polygon is defined as the average value of allthe points comprising the perimeter of the planar polygon. In the caseof a convex polygon, the centroid of the polygon always lies within thearea enclosed by the polygon perimeter. For the levitation stabilizingstructure to be most effective it is required that the centroid of thebarrier structure comprising the levitation stabilizing structure liewithin the interior impingement area of the levitation stabilizingstructure and a convex polyhedral shaped levitation stabilizingstructure satisfies this requirement. Thus, a levitation stabilizingstructure in the form of a convex polygonal barrier structure with aproper rotational axis of symmetry, C_(n) with n≥2, provides a means tokeep the pneumatically levitated moveable substrate in a known positionand provides a means for producing in-situ correcting forces that canimpede undesirable horizontal substrate movement. Undesirable horizontalsubstrate movement includes horizontal lateral substrate movement thatcan occur as a result of normal fluctuations in critical pneumaticvariables during pneumatic levitation. It has been discovered duringexperimentation with levitation stabilizing structures employingdifferent convex polygon shapes that convex polygons with a properrotational axis of symmetry, C_(n) where n≥2 can result in pneumaticlevitation where the substrate is relatively motionless duringlevitation with a single orthogonal jet employed as a means forsupplying the fluid for pneumatic levitation. Furthermore, it has alsobeen observed that levitation stabilizing structures employing differentconvex polygon shapes with a proper rotational axis of symmetry, C_(n)where n=2 can result, under certain conditions in pneumatic levitationwhere the substrate may exhibit rotation about the axis of rotationsymmetry during levitation, especially when the orthogonal jet does notexactly align with the centroid of the levitation stabilizing structure.It is known that many processes show improved spatial uniformity whenthe substrate is rotated while the process is carried out. Thus, it hasnow been discovered by observation that substrate rotation can beachieved through the use a levitation stabilizing structure with the useof only an orthogonal jet although the exact origins of this unexpectedeffect remain unexplained. Unlike the art disclosed in U.S. Pat. Nos.5,470,420 and 8,057,602 no tilted jets are required to produce substraterotation during pneumatic levitation and no physical stops are requiredto force the substrate to remain in a localized region. This is adistinct advantage because it simplified equipment design for improvingthe uniformity of processes employing pneumatic levitation.

Alternatively, in another embodiment of the invention, the levitationstabilizing structure or rotationally symmetric convex polygonal barrierstructure will fulfill its function with non-orthogonal jets also, andis most effective when tilted, non-orthogonal jets are arranged in asymmetrical arrangement so the symmetrical barrier structure of thelevitation stabilizing structure can produce the balanced forcesnecessary to produce a condition where the substrate remains in a steadystate or equilibrium position about a rotational axis during momentumtransfer from the tilted jets. When non-orthogonal jets emanate from thestationary gas emitting support in an appropriate symmetricalarrangement, rotation of the moveable substrate can be achieved duringpneumatic levitation by momentum transfer from the gaseous fluid to thepneumatically levitated moveable support as described in U.S. Pat. Nos.5,470,420; 5,492,566; 5,967,578; and 8,057,602 B2. Without wishing to bebound by theory, it is believed that it is preferable that the centroidof the levitation stabilizing structure be aligned with the centroid ofthe polyhedral shape defined by the arrangement of the non-orthogonalfluid collimating conduits in the stationary fluid emitting support,each fluid collimating conduit position being considered as a vertex ofthe polyhedra. When non-orthogonal jets are used for fluidic levitationof a moveable substrate it is preferable that the stationary fluidemanating support through which fluid will flow contain two or morefluid collimating conduits (for example, orifices, nozzles or bores) sothat two or more non-orthogonal tilted jets emanate from the surface ofthe stationary fluid emanating support. When a circular levitationstabilizing structure is present on the moveable substrate and islocated on the moveable substrate surface opposing the gas emittingstationary support with an arrangement of tilted jets similar to thoseas described in U.S. Pat. No. 5,470,420 then stable high speed rotationof a pneumatically levitated sample can be observed. In one embodimentstable substrate rotation with substrate rotational speeds in excess of500 rpm are observed during pneumatic levitation of a moveable substratewith an annular levitation stabilizing structure when employing asymmetric arrangement of tilted jets to supply fluid to achieveBernoulli air flow pneumatic levitation of the substrate. While rotationwith pneumatic levitation is suitable and desirable for someapplications, it is recognized that the fabrication of the stationarysupport containing tilted jets is complicated and the uniformity ofradial flow during pneumatic levitation is disrupted by the use oftilted jets; however, a moveable substrate with a levitation stabilizingstructure exhibiting excellent positional stability with arrays oftilted jets during pneumatic levitation or pneumatically levitatedrotation is particularly useful for processes involving cleaning ofsurfaces such as, for example, the processes described in U.S. Pat. Nos.5,492,566 and 5,967,578 as well as for certain types of depositionprocesses. In another embodiment, both tilted and orthogonal fluidcollimating conduits are used. In one embodiment, the stationary supportfor a pneumatic levitation apparatus includes a plurality of fluidcollimating conduits through which a plurality of fluids flow, whereintwo of the plurality of fluid collimating conduits are tilted withrespect to the substrate such that the direction of the fluid flowthrough the tilted fluid collimating conduits is tilted with respect tothe substrate and one of the plurality of fluid collimating conduits isorthogonal to the substrate such that the direction of the fluid flowthrough the orthogonal fluid collimating conduits is orthogonal to thesubstrate. In one embodiment, the plurality of fluids are columnarcompound fluids. In another embodiment, the stationary support includesa plurality of fluid collimating conduits, wherein two of the pluralityof fluid collimating conduits are tilted with respect to the substrateand through which an inert fluid flows and one of the plurality of fluidcollimating conduits is orthogonal to the substrate and through whichthe compound fluid flows. In a further embodiment, two tilted fluidcollimating conduits are arranged symmetrically around the orthogonalfluid collimating conduit. In another arrangement, two of the pluralityof fluid collimating conduits are tilted with respect to the substrateand an inert fluid flows through them. One of the plurality of fluidcollimating conduits is orthogonal to the substrate and a columnarcompound fluid flows through it to form a columnar compound fluid jet.In another embodiment, the tilted fluid collimating conduits arearranged symmetrically around the orthogonal fluid collimating conduit.

Referring to FIG. 4, fluidic levitation of moveable substrate withlevitation stabilizing structure of various sizes, masses and areas canbe accomplished by careful design of the fluid-emitting stationarysupport surface through which fluid will flow as well as adjustment ofthe fluid pressure. For example, the pneumatic levitation of a largerarea planar substrate with levitation stabilizing structure can beaccomplished by adjusting the pneumatic pressure of the orthogonalgaseous fluid jet emanating from the stationary support to achievesufficient fluid flow to enable fluidic levitation. In anotherembodiment, the stationary fluid emitting support can be equipped withadditional fluid-emitting fluid collimating conduits, tilted ororthogonal, to enable the fluidic levitation of a larger support.

Referring to FIG. 27, the fluid emitting stationary support 12 locatedinside chamber or enclosure 60 has at least one orthogonal fluidcollimating conduit 14 and at least 2 tilted fluid collimating conduits15 through which fluids pass. The fluid jets emanating from the fluidcollimating conduits 14 and 15 impinge on moveable substrate 10 withlevitation stabilizing structure 30 in the interior impingement area 35enclosed by the levitation stabilizing structure interior walls 38.Proper rotational axis 40 is shown as a dotted line to illustrate thesymmetry associated with the two tiled fluid collimating conduits 15 inthe stationary fluid emitting support. An axis of order n of properrotation, C_(n), is an axis of rotational symmetry essentiallyorthogonal to the moveable substrate surface. In one embodiment thestationary fluid emitting support through which fluid will flow forpneumatic levitation of a large area planar moveable substrate withlevitation stabilizing structure is comprised of a non-porous block withat least one fluid collimating conduit for producing at least oneorthogonal jet and at least two fluid collimating conduits for producingat least two tilted jets, said tilted jets being related to each otherusing a proper rotation axis passing through the orthogonal jet. Inanother embodiment, the tilted jets are oriented so that the projectionsof the fluid velocity vector from the tilted jet on the stationarysupport surface are related by a proper rotation symmetry elementlocated at the orthogonal jet. For example, if the projected velocityvector from a tilted jet onto the stationary support viewed parallel tothe proper rotation axis normal to the stationary support surface andpassing through point (0,0) extends from the point (0,0) to the point(x,y) then the projected velocity vector that is related by C₂ properrotation around the C₂ rotational axis at (0,0) extends from the point(0,0) to the point (−x,−y). The rotation operation around the rotationalsymmetry element passing through (0,0) takes every point (x,y) of thevector projection of the tilted jet velocity vector onto the stationarysupport surface and relates it to (−x,−y) by rotational symmetry. Twotilted jets related by rotation around a proper rotational axis of order2 or greater that is normal to the stationary support surface andlocated at the position of the orthogonal jet are required to maintainbalanced forces on the levitation stabilizing structure and eliminatelateral motion of the substrate during pneumatic levitation.

In another embodiment, the fluid-emanating stationary support iscomprised of at least one orthogonal jet and at least one flow controlstructure and the flow control structure providing a means forexhausting radial flow from at least one orthogonal jet emanating fromthe stationary support surface.

The present invention is usefully applied to a variety of moveablesubstrate 10 sizes. For example substrates as small as 50 microns indiameter can incorporate a levitation stabilizing structure to provideflow modulation and pressure control of fluid flows entering into MEMSmicro-fluidic devices to deposit atomic this film layers. The presentinvention can also be used for conventionally sized silicon wafersubstrates ranging in size from 50 mm, 100 mm, 150 mm, 200 mm. and 300mm in diameter. In an alternative example, substrates as large as 500 mmlike large silicon wafers can be employed with the present invention.

FIGS. 5a through 5h show plan views of several different types oflevitation stabilizing structures 30 on moveable substrates 10. Althoughthe examples shown in FIGS. 5a-5h show planar substrates that are eithercircular or rectangular, it is recognized that the invention can be morebroadly implemented in moveable substrates having other arbitraryshapes, forms, and topographies. In FIGS. 5a through 5h , point 40, whenmarked in FIGS. 5a-5f , is the location of intersection of a properrotation axis of symmetry that is normal to the plane of the figure andpasses through point 40 in the plane of the illustrated plan view. Theproper rotation axis 40 also passes through the centroid of thepolyhedral shape that defines the interior impingement area of thelevitation stabilizing structure.

FIG. 5a shows a plan view of a moveable circularly shaped substrate 10upon which an annular or circular levitation stabilizing structure 30has been fabricated. Point 40 is the location of the proper rotationaxis of symmetry for the levitation stabilizing structure 30 which is aC_(n) axis where n=∞. The proper rotation axis of symmetry intersectingpoint 40 in FIG. 5a is a C_(∞) proper rotation axis. FIG. 5a illustratesa plan view of a levitation stabilizing structure that is reduced topractice in examples 2, 3, and 4.

FIG. 5b is a plan view of a moveable circularly shaped substrate 10 uponwhich a triangular levitation stabilizing structure 30 has beenfabricated. Point 40 is the location of the proper rotation axis ofsymmetry for the levitation stabilizing structure 30 which is a C_(n)axis where n=3. The proper rotation axis of symmetry intersecting theplan view at point 40 in FIG. 5b is a C₃ proper rotation axis.

FIG. 5c is a plan view of a moveable circularly shaped substrate 10 uponwhich a rectangular levitation stabilizing structure 30 has beenfabricated. Point 40 is the location of the proper rotation axis ofsymmetry for the levitation stabilizing structure 30 which is a C_(n)axis where n=2. The proper rotation axis of symmetry intersecting theplan view at point 40 in FIG. 5c is a C₂ proper rotation axis. FIG. 56cillustrates a plan view of a levitation stabilizing structure that isreduced to practice in examples 5 and 6.

FIG. 5d is a plan view of a moveable circularly shaped substrate 10 uponwhich a convex polygonal levitation stabilizing structure 30 has beenfabricated. The levitation stabilizing structure 30 has the shape of aconvex polygon with no proper rotation axis of symmetry. As a result,point 40 is absent although the centroid of the polygon in FIG. 5d stilllies within the perimeter of the polygon.

FIG. 5e is a plan view of a moveable rectangularly shaped substrate 10upon which an ellipse-shaped oval levitation stabilizing structure 30has been fabricated. Point 40 is the location of the proper rotationaxis of symmetry for the levitation stabilizing structure 30 which is aC_(n) axis where n=2. The proper rotation axis of symmetry intersectingthe plan view at point 40 in FIG. 5e is a C₂ proper rotation axis.

FIG. 5f is a plan view of a moveable circularly shaped substrate 10 uponwhich a concave polygonal levitation stabilizing structure 30 has beenfabricated. The levitation stabilizing structure 30 has the shape of aconcave polygon with no proper rotation axis of symmetry. As a result,point 40 is absent although the centroid of the polygon in FIG. 5f stilllies within the perimeter of the polygon.

FIG. 5g is a plan view of a moveable rectangularly shaped substrate 10upon which a rectangular levitation stabilizing structure 30 has beenfabricated. Point 40 is the location of the proper rotation axis ofsymmetry for the levitation stabilizing structure 30 which is a C_(n)axis where n=2. The proper rotation axis of symmetry intersecting theplan view at point 40 in FIG. 5g is a C₂ proper rotation axis. FIG. 5eillustrates a plan view of a levitation stabilizing structure whosemoveable substrate elements are reduced to practice in example 12.

FIG. 5h is a plan view of a moveable square shaped substrate 10 uponwhich a square levitation stabilizing structure 30 has been fabricated.Point 40 is the location of the proper rotation axis of symmetry for thelevitation stabilizing structure 30 which is a C_(n) axis where n=4. Theproper rotation axis of symmetry intersecting the plan view at point 40in FIG. 5e is a C₄ proper rotation axis. FIG. 5h illustrates a plan viewof a levitation stabilizing structure whose moveable substrate elementsare reduced to practice in example 10.

FIGS. 6a through 6e illustrate the application of a levitationstabilizing structure to a non-planar moveable substrate having threedimensional surface shape and topography. FIG. 6a is a cross-sectionalview of the prior art from WO 96/29446 showing a spherical moveablesubstrate 10 positioned over a gas-emanating stationary support 12containing a fluid collimating conduit 14 that diverges as it approachesthe surface of the spherical moveable substrate 10. WO 96/29446describes the use of the configuration shown in FIG. 6a for pneumaticlevitation of carbon spheres for the purpose of producing uniformcoatings of rhenium metal on the sphere using thermal decomposition of avolatile rhenium metal containing precursor on the pneumaticallylevitating spherical substrate 10. Although the stable pneumaticlevitation of spherical objects can be achieved with a suitably largevolumetric gas flow, the edges of the fluid collimating conduit 14 onthe gas-emanating stationary support 12 provide a physical stop toprevent the moveable substrate 10 from shifting out of position duringpneumatic levitation. During pneumatic levitation the spherical moveablesubstrate rotates freely and the orientation of the axis of rotationvaries at random, thereby allowing the production of a uniformdeposition through the thermal decomposition of a volatile rhenium metalcontaining precursor. FIG. 6b is a cross-sectional view of oneembodiment of the present inventive method applied to the configurationdisclosed in WO 96/29446 wherein a levitation stabilizing structure 30with a proper rotation axis of symmetry 40 has been fabricated andattached to the surface of the spherical moveable substrate 10 and theinterior walls of said levitation stabilizing structure 30 areoptionally normal to the surface of the spherical moveable substrate.The spherical moveable substrate 10 is positioned above the stationarysupport 12 and fluid collimating conduit 14 so that the levitationstabilizing structure 30 opposes the gas-emanating stationary support12. The levitation stabilizing structure 30 allows the sphericalmoveable substrate 10 to rotate freely about the proper rotation axis ofsymmetry during pneumatic levitation thereby providing a way ofselectively coating one or more portions of the spherical moveablesubstrate 30 in a uniform fashion during the deposition process. FIG. 6cis a cross-sectional view of another embodiment of the present inventivemethod applied to the configuration disclosed in WO 96/29446 wherein alevitation stabilizing structure 30 with a proper rotation axis ofsymmetry 40 has been fabricated and attached to the surface of thespherical moveable substrate 10 and the interior walls of saidlevitation stabilizing structure 30 are optionally normal to the surfaceof the spherical moveable substrate. The spherical moveable substrate 10is positioned above the stationary support 12 and fluid collimatingconduit 14 so that the levitation stabilizing structure 30 opposes thegas-emanating stationary support 12. The stationary fluid emittingsupport structure 12 is modified to follow the surface contours ofspherical moveable substrate 10 in a conformal-wise manner and thestationary fluid emitting support structure 12 further provide a singleorthogonal fluid jet for the purpose of pneumatic levitation of moveablesubstrate 10. The levitation stabilizing structure 30 allows thespherical moveable substrate 10 to rotate freely about the properrotation axis of symmetry during pneumatic levitation thereby providinga way of selectively coating one or more portions of the sphericalmoveable substrate 30 in a uniform fashion during the depositionprocess. FIGS. 6d and 6e show two plan views of two embodiments of themoveable spherical substrate with a levitation stabilizing structurecompatible with the apparatus configurations shown in FIGS. 6b and 6c .The plan view is directly down the proper rotation axis of symmetry ofthe levitation stabilizing structure so that the rotational symmetry ofthe levitation stabilizing structure 30 can be seen. FIG. 6d shows thata circular levitation stabilizing structure 30 on the spherical moveablesubstrate 10 with a proper rotational axis of symmetry 40 that is aC_(∞) axis. FIG. 6e shows that a pentagonal levitation stabilizingstructure 30 on the spherical moveable substrate 10 with a properrotational axis of symmetry 40 that is a C₅ axis.

Thus, a further advantage of method of fluidic levitation employing alevitation stabilizing structure is the fluidic levitation ofarbitrarily shaped substrates and the processing of selective portionsof the surface area of said arbitrarily shaped substrates. In theembodiments shown above in 6 a through 6 e, the levitation stabilizingstructure can be formed on arbitrarily shaped substrate thereby enablingpneumatic levitation of the arbitrarily shaped substrate when the planeof the levitation stabilizing structure is positioned normal to andfacing an orthogonal jet emanating from a stationary support. Asmentioned previously, the levitation stabilizing structure additionallyenables the use of pneumatic levitation with, for example, planarsubstrates that are shaped like circles, triangles, squares, and otherpolygonal shapes. The levitation stabilizing structure is particularlyuseful for pneumatic levitation of silicon wafers that are essentiallycircular shaped and are additionally marked with a flat or notch so thatthe wafer is not perfectly symmetric. Wafers marked with a flat can beconsidered to be arbitrarily shaped substrates and the levitationstabilizing structure is particularly useful for pneumatic levitation ofsamples of this type. Additionally, the levitation stabilizing structurecan be employed with three dimensional moveable substrates, saidsubstrates being planar or non-planar, to enable processing of selectedregions on the substrate surface.

In another embodiment, the levitation stabilizing structure fabricatedupon a moveable substrate includes a material layer having one surfacecontacting the moveable substrate surface and having a thickness greaterthan 20 microns; wherein the material layer is patterned to create aconcave or convex polygonal shaped depressed area bounded by a thicknessof the material layer, the height of the boundary wall around thedepressed area as measured normal to the tangent plane of the moveablesupport surface being essentially equal to the thickness of the materiallayer; the centroid of the polygon shaped depressed area lying withinthe polygon shaped interior impingement area of the patterned materiallayer; the surface area of the polygonal shaped interior impingementarea defined by the patterned material layer being at least 4 timeslarger than the cross-sectional area of the orthogonal jet impinging onsaid area.

FIG. 7a is an isometric view of an embodiment of a levitationstabilizing structure 30 fabricated on a planar moveable substrate 10where at least one surface of levitation stabilization structure 30 isin contact with moveable substrate 10. FIG. 7a shows the moveablesubstrate surface normal 16, levitation stabilizing structure 30comprised of a patterned material layer, levitation stabilizingstructure interior wall 38, and polygonal shaped interior impingementarea 35 bounded by a thickness of the material layer comprisinglevitation stabilization structure 30 that is characteristic of theheight of the interior wall 38. The levitation stabilizing structure 30overlays and is in contact with the moveable substrate 10. In oneembodiment the levitation stabilizing structure 30 overlays and is incontact with the moveable substrate 10 except in the interiorimpingement area. In another embodiment the material layer of thelevitation stabilizing structure 30 overlays and is in contact with themoveable substrate 10 and the thickness of the material layer comprisingthe levitation stabilizing structure is reduced and is thinner in theinterior impingement area so that the height of the interior wall of thelevitation stabilizing structure 38 is determined by the differencebetween the thickness of the material layers inside the interiorimpingement area and outside the interior impingement area. The heightor thickness of the material layer at any point on the substrate surfaceis measured in relation to the substrate surface by perpendicular 32(not shown) along moveable substrate surface normal 16. In someapplications it can be advantageous that the composition of the exposedsurface comprising the polygonal shaped depressed interior impingementarea 35 be the same as the composition of the material layer of thelevitation stabilization structure 30. In another embodiment, thepolygonal shaped depressed interior impingement area 35 of FIGS. 7a and7b can be fabricated so that the exposed surface area of the polygonalshaped depressed interior impingement area 35 has a differentcomposition from that of the surface of the moveable substrate 10 or adifferent composition from the levitation stabilizing structure 30. Inanother embodiment of the inventive method, the polygonal shapeddepressed interior impingement area 35 of FIGS. 7a and 7b can befabricated so as to allow the surface of moveable substrate 10 to beexposed in the interior impingement area.

FIG. 7b shows a plan view of one embodiment of a levitation stabilizingstructure 30 comprised of material layer fabricated on a moveablesubstrate 10, levitation stabilizing structure interior wall 38,polygonal shaped interior impingement area 35, said interior impingementarea 35 containing the centroid region 42 of the polygonal shape ofinterior impingement area 35, showing that the centroid region 42 lieswithin the interior walls 38 of the polygonal shaped depressed area ofinterior impingement area 35. The shape of the polygonal shapeddepressed area that corresponds to the interior impingement area 35 ofthe levitation stabilizing structure and is shown in FIGS. 7a and 7b isirregular and concave. The polygonal shape of the interior impingementarea 35 is not restricted to concave polyhedral shapes, nor is thepolygonal shape of the interior impingement area restricted to thosepolygonal shapes shown in FIGS. 5a through 5f . Without wishing to bebound by theory, it is believed that a criteria for choosing aparticular polyhedral shape for the interior impingement area of thelevitation stabilizing structure is that the centroid of the polyhedralshape must lie within the area of the polyhedral shape. In other words,it is believed that the best functioning polyhedral shaped interiorimpingement areas have their centroid located in the interior area ofthe polyhedra that is defined by the area enclosed within thecircumference of the polyhedra shape. Furthermore, the moveablesubstrate 10, shown as a planar object in FIGS. 7a and 7b , is notrestricted to objects with planar surfaces. The general applicability ofthe levitation stabilizing structure to non-planar substrates has beenpreviously shown in FIGS. 6a through 6 e.

According to the description of FIGS. 7a and 7b , then, in oneembodiment, the levitation stabilizing structure can be a continuouspatterned layer of a single composition. In another embodiment thelevitation stabilizing structure can be comprised of a plurality oflayers including a continuous patterned material layer of a singlecomposition, an adhesive layer, and an adhesion promoting layer whereinthe levitation stabilizing structure is attached, to an underlyingmoveable substrate, the continuous nature of the levitation stabilizingstructure not allowing exposure of the surface of the underlyingmoveable substrate through the levitation stabilizing structure materiallayer. In another embodiment, a multilayer levitation stabilizingstructure can be comprised of a non-continuous patterned material layerof a single composition and at least one adhesion promoting layers thatprovide a means to attach the levitation stabilizing structure to anunderlying moveable substrate, the dis-continuous or non-continuousnature of the levitation stabilizing structure thus allowing exposure ofthe surface of the underlying moveable substrate through the levitationstabilizing structure. In a third embodiment, the material layer locatedin interior impingement area of the levitation stabilizing structure canbe of a composition which is different from either the moveablesubstrate or the material layer of the levitation stabilizing structure.

Thus, in one embodiment the levitation stabilizing structure iscomprised of a material layer having one side contacting the moveablesubstrate surface and having a thickness greater than 20 microns;wherein the material layer is patterned so as to create a depressioncorresponding to an interior impingement area; the walls of saiddepression being essentially normal to the moveable support surface; theheight of the walls of the depression being essentially equal to thedepth of the polygonal shaped depressed area into the material layer;the shape of the depression being the shape of a polygon whose centroidlies within the polygonal shape of the depression; preferably a convexpolygon possesses at least three sides wherein the convex polygon has atleast one axis of proper rotation, C_(n), said axis of rotationalsymmetry being essentially orthogonal to the moveable substrate surfaceand the plane containing the material layer; wherein the order orcoefficient, n, of the axis of proper rotation is equal to or greaterthan 2; the area of the depression defining the convex polygon whoseperimeter corresponds to the interior walls of the interior impingementarea in the material layer being at least 4 times larger than thecross-sectional area of the orthogonal impinging jet employed duringfluid levitation.

Characteristic features of the levitation stabilizing structure on asubstrate such as, for example, the width of the levitation stabilizingstructure, can be determined by the process into which the fluidlevitation technology will be integrated. For example, the levitationstabilizing structure can be used to mask off just a portion of themoveable substrate surface so that only a particular portion of thesurface is exposed to the levitating gas flow whilst all other substratesurfaces are passivated by the material layer of the levitationstabilizing structure—the inventive concept shown in FIGS. 7a and 7b .In practice, the minimum width of the interior walls 38 of thelevitation stabilizing structure is determined by the mechanicalproperties of the material layer employed to fabricate the levitationstabilizing structure and the thickness required to sustain amechanically rigid barrier to the fluidic pressures encountered duringfluidic levitation. A levitation stabilizing structure havinginsufficient rigidity may exhibit unpredictable behavior duringlevitation processes, said behavior characterized by interior walls ofthe interior impingement area that deflect, buckle, bend, or collapsewhen exposed to fluidic flow under fluidic levitation conditions therebyrendering the levitation stabilizing structure useless. The twocontemplated fluidic flows are pneumatic flow involving compressiblefluids such as gasses and hydraulic flow involving non-compressible orincompressible fluids such as liquids.

In one embodiment the levitation stabilizing structure is fabricated onan essentially planar substrate. The planar substrate, however, does nothave to be a rigid or self-supporting substrate and may comprise aflexible material that remains in a planar configuration when supportedby a gas film generated on a planar surface or some other planar supportstructure.

The thickness of the material layer for the LSS necessary to achieve adesired level of fluidic levitation performance depends on the mass anddimensions of the moveable substrate as well as the total gas flowemployed during fluidic levitation. For example, an LSS for amicromechanical gas flow restraining device having a moveable substratediameter of 100 microns and employing a single orthogonally impingingjet on the moveable substrate may require a material layer thickness forthe LSS of less than 50 microns whilst the application of an LSS for thepurpose of pneumatic levitation of a 150 mm silicon wafer with a singleorthogonal jet emanating from a stationary gas emitting support mayrequire a material thickness for the LSS of between 130 and 300 microns.

The material layer of the levitation stabilizing structure (LSS)fabricated upon a moveable substrate can be formed using additiveprocesses like, for example, deposition processes, to form a materiallayer having properties appropriate for substrate type and thelevitation application. For example, the levitation stabilizingstructure can be formed on the moveable substrate using any methodfamiliar to those skilled in the art of additive material processing.Methods for additive substrate processing include deposition methodssuch as physical vapor deposition, chemical vapor deposition,sputtering, electroplating, electroless deposition, electroforming;additive methods like lamination of an LSS comprised of one or morematerial layers using adhesion promoting layers with the aid oftemperature and/or pressure; and printing methods of all types includinglithography, screen printing, inkjet printing, 3 dimensional inkjetprinting; 3 dimensional printing with extruded polymers; 3 dimensionalprinting employing sinterable materials; stenciling, painting, epitaxialgrowth, spin coating or any other method of additive material depositionknown in the art. Alternately, the LSS can be formed by patterning apre-existing material layer prepared, for example by additiveprocessing. The patterning of the pre-existing material layer can beaccomplished using subtractive processes familiar to those skilled inthe art of subtractive material processing to form a patterned materiallayer whose features correspond to those of a levitation stabilizingstructure having properties that are appropriate for the substrate typeand the levitation application. Many useful subtractive processesinclude the use of masks to ensure that material is removed from thematerial layer only in the desired regions. Examples of subtractiveprocesses employed to form a levitation stabilized structure includevapor phase etching methods, liquid phase etching methods, plasmaassisted etching methods, subtractive machining and micromachiningmethods including spark machining and waterjet machining methods,electrostripping methods including patterned electrostripping with theuse of passivation layers and masks, subtractive electrochemicalmachining methods using specially shaped electrodes and masks,subtractive material processing involving patterning of positive andnegative photosensitive resist layers, and other subtractive materialprocessing methods for processing and patterning material layers.Furthermore, it may sometimes be desirable that the LSS can befabricated as an integral part of the substrate itself by employingknown technologies used to fabricate articles of complex shape suchconventional machining processes, injection molding, extrusion,stamping, hydroforming, electroforming, multistep deposition andpatterning of material layers using process steps found in themanufacture of integrated circuits, specialized micromachining methodssuch variants of chemical mechanical polishing as well as othermicromachining methods employed for the manufacture ofmicroelectromechanical systems (MEMS) and devices, and the like. The LSSmay thus be formed in a singular piece integrated with the substrate forsubsequent processing applications. In some embodiments the interiorimpingement area of the LSS can be backfilled with an additional thinmaterial layer resulting in a complex multilayer structure as previouslydescribed.

FIG. 8 shows a cross-sectional view of one embodiment of a multilayerlevitation stabilizing structure 30 comprised of a material layer 46overlaying and contacting an adhesion promoting layer 44, the adhesionpromoting layer being positioned and interposed between and in contactwith a surface of the material layer 46 and in contact with a surface ofthe moveable substrate 10. The adhesion promoting layer 44 is shown as adiscontinuous layer in FIG. 8; however, the adhesion promoting layer 44in FIG. 8 may optionally be a continuous layer.

In another embodiment, the levitation stabilizing structure 30 can beformed externally, like a gasket fabricated from a material layer in theappropriate shape and thickness, aligned and adhered to the moveablesubstrate using an adhesive layer or adhesion promoting layer whendesired. The levitation stabilizing structure can be a removable elementthat can be added or removed from the moveable substrate as desired. Thelevitation stabilizing structure can be adhered to the moveablesubstrate by any means familiar to those skilled in the art of adhesion,joining, and gluing; for example, an adhesive promoting glue layer canbe employed to attach the levitation stabilizing structure to themoveable substrate thereby providing a moveable substrate with anattached levitation stabilizing structure. In some cases, an externallyfabricated levitation stabilizing structure that is attached to themoveable substrate with an adhesive layer can be a preferred method ofpreparing a moveable substrate with a levitation stabilizing structurebecause the choice of adhesive or adhesion method may allow easyapplication of the levitation stabilizing structure to the moveablesubstrate or optional removal of the levitation stabilizing structurefrom the moveable substrate surface. Various types of adhesion promotinglayers can be employed to attach a levitation stabilizing structure to amoveable substrate for the purposes of fluidic levitation. In oneembodiment, the adhesive layer can be comprised of a pressure sensitive,removable adhesive possessing sufficient bonding strength for use inlevitation applications. In another embodiment the adhesive layer can becomprised of a more permanent, non-removable type of adhesive,optionally pressure sensitive, possessing sufficient bonding strengthfor use in levitation applications. In one embodiment, a pressuresensitive adhesive that increases its adhesive strength upon exposure toheat can be used to adhere the levitation stabilizing structure to amoveable substrate. In another embodiment, a pressure sensitive adhesivethat loses its adhesive strength upon exposure to heat can be used toadhere the levitation stabilizing structure to a moveable substrate. Inanother embodiment, an adhesive that is optionally pressure sensitiveand increases its adhesive strength upon exposure to ionizing radiationcan be used to adhere the levitation stabilizing structure to a moveablesubstrate. In a further embodiment, an adhesive that is optionallypressure sensitive and loses its adhesive strength upon exposure toionizing radiation can be used to adhere the levitation stabilizingstructure to a moveable substrate. The aforementioned embodimentsexemplify the general use of adhesive layers with the levitationstabilizing structure are not meant to be restrictive in any way as theinventors recognize that other adhesive layers can be applicable andfall within the contemplated spirit of the invention.

In a further embodiment the levitation stabilizing structure ismechanically and releasably attached to the moveable substrate tofacilitate ease of moveable substrate assembly without the use ofsupplemental adhesive layers that chemically bond the levitationstabilizing structure to the moveable substrate. In one embodiment thelevitation stabilizing structure is mechanically and releasably attachedto the moveable substrate through fasteners that can be tightened orloosened to install or remove the levitation stabilizing structure fromthe moveable substrate. In another embodiment spring loaded fastenersare used to mechanically install the levitation stabilizing structure.In one embodiment magnetic fasteners are used to mechanically andreleasably attach the levitation stabilizing structure to the moveablesubstrate. In one embodiment interlocking mechanical features are usedto mechanically fasten and releasably attach the levitation stabilizingstructure to the moveable substrate. In a further embodiment, miniaturelatches are employed to mechanically and releasably attach thelevitation stabilizing structure to the moveable substrate. In anotherembodiment, the movable substrate includes a backing plate and aclamping structure to mechanically and releasably attach the levitationstabilizing structure to the moveable substrate.

As mentioned previously, the LSS can be a multilayer structure formedfrom a wide variety of materials, and the subsequent use of the LSS forpneumatic levitation during substrate processing is part of the criteriadetermining whether the LSS is compatible with the underlying substrate.The LSS can be fabricated from the same material as the substrate,including the material of the substrate itself, or it can be fabricatedfrom a material of different chemical composition and may include one ormore adhesion promoting layers to facilitate the adhesion of the LSS tothe underlying substrate. For example, wafer bonding can be used, tobond an ultrathin wafer to a LSS made from the same material so that theultrathin wafer can be processed in a non-contact levitated manner.

In one embodiment of the levitation stabilizing structure, the LSS canbe formed using a curable material with cross-linking agents. Thecurable material can be photosensitive and the LSS can be formed bycoating the moveable substrate with a curable layer; exposing thecurable layer to patterned radiation to form a patterned cured layer;and removing the uncured curable layer to form the levitationstabilizing structure. In a particular embodiment of the levitationstabilizing structure, the LSS can be formed using positive or negativephotoresist, employing liquid photoresist. An example of a liquidphotoresist that can be used to form a levitation stabilizing structureis the negative photoresist that is commercially available as MicroChemSU8 2050. The liquid photoresist can be applied by spin coating or othermethods to form a material layer on the surface of the moveablesubstrate. The photoresist layer can be further be processed bypatterning the photoresist material layer to form a polygon shapeddepression of desired area and depth, said polygon being either convexor concave, where the centroid of the polygon lies within the area ofthe polygon defined by the surface area of the polygon lying within theperimeter of the polygon. In the embodiment of the fabrication of alevitation stabilizing structure using a material layer comprisedessential of a patterned and developed photoresist, it is clear that thefabrication of the levitation stabilizing structure is compatible withfabrication methods normally employed in integrated circuit manufactureand is readily implemented in the semiconductor integrated circuitfabrication workflow.

In another embodiment of the invention, the LSS can be formed using amaterial layer 46 comprised of positive or negative photoresist,employing dry film photoresist. Dry film photoresist can be applied tothe moveable substrate using lamination methods or vacuum laminationmethods onto the surface of the moveable substrate. An example of a dryfilm photoresist that can be used for fabricating a levitationstabilizing structure is DuPont WBR2000 series dry resist film. Thephotoresist layer can be further be processed by patterning thephotoresist material layer to form a polygon of appropriate area, saidpolygon being either convex or concave, where the centroid of thepolygon lies within the area of the polygon defined by the surface areaof the polygon lying within the perimeter of the polygon. In the exampleof the fabrication of a levitation stabilizing structure using amaterial layer comprised essentially of a patterned and developed dryfilm photoresist, it is clear that the fabrication of the levitationstabilizing structure is compatible with fabrication method normallyemployed in integrated circuit manufacture and is readily implemented inthe semiconductor integrated circuit fabrication workflow.

Additionally, the use of photopatternable photoresist layers for thefabrication of levitation stabilizing structures is compatible with theprocess flows employed in the fabrication of many microelectromechanicalsystems (MEMS).

In some cases it can be advantageous to have a permanent levitationstabilizing structure and the material layer 46 of such structures canbe prepared by numerous methods including those described above, as wellas by using chemically stable photoresist materials such as epoxy basedphotoresists. In other cases, the levitation stabilizing structure onthe moveable substrate may need to be transient and removable—onlypresent for a single processing step. Removable levitation stabilizingstructure can be prepared using materials that can be chemically orphysically stripped after use. Examples of removable levitationstabilizing structures are levitation stabilizing structures preparedfrom thick dry film photoresists or prepared using electroformingdeposition methods. Electroformed levitation stabilizing structure canbe removed by electrostripping or another material removal process, suchas chemical dissolution.

In another embodiment, 3-dimensional printing methods can be used tofabricate the levitation stabilizing structure 30 on a moveablesubstrate 10 with or without the aid of an adhesion promoting layer 44and the use of 3 dimensional printing methods may provide additionaleconomy with respect to material and fabrication costs of the levitationstabilizing structure.

The disclosed inventive method of fluidic levitation employing alevitation stabilizing structure overlaying and in contact with amoveable substrate is useful for stabilizing fluid levitation of amoveable substrate with both compressible and non-compressible orincompressible fluids. Flexible substrates as well as rigid substratescan be fluidically levitated with a levitation stabilizing structure.Fluidic levitation is generally applicable to moveable substrates ofmany different types including plastics, semiconductor materials,insulator materials, electrically conducting materials, magneticmaterials of all types (meaning ferromagnetic and anti-ferromagnetic,diamagnetic, paramagnetic, and other types of magnetic materials) andother substances that are solid and dimensionally stable under pneumaticlevitation conditions. Of course, the composition of the material layer46 must also be carefully considered with respect to the nature of thefluid employed during levitation so that the fluid does not adverselyinfluence the integrity of the material layer employed to fabricate thelevitation stabilizing structure. Those skilled in the art of fluidmechanics will recognize that the levitation stabilizing structurepresented here is equally applicable to both pneumatic and hydrauliclevitation and thus the use of the levitation stabilizing structure withboth pneumatic and hydraulic levitation falls within the contemplatedscope of the invention. The advantages of incorporating pneumaticlevitation during substrate processing are many and some of theadvantages have been previously enumerated in U.S. Pat. No. 5,370,709wherein the use of a “suction plate” that enables substrate levitationby Bernoulli gas flow is described. The moveable substrate does not comein contact with any member of the processing equipment so no particlesare generated. This is not strictly true in the case of U.S. Pat. No.5,370,709 because the apparatus described therein specifically usesphysical stops to prevent substrate motion. The use of a levitationstabilizing structure of the present invention completely removes anyphysical contact to the moveable substrate during levitation. The gasexchange in the space between the stationary support and the moveablesubstrate is extremely rapid, thus contamination such as autodoping orcontamination from other forms of contaminating outgassing can beminimized during processing. Process times associated with gas exchangesuch as purge steps to ensure gas purity during processing can beminimized because of the small volume between the moveable substrate andthe gas-emanating stationary support. The rapid gas exchange due to highgas velocities combined with small reaction volumes leads to anadvantage in gas consumption. The sample is thermally isolated by alayer of gas and, as a result, temperature control can be extremelyefficient with a minimum of power being required to achieve processtemperature. Cooling is efficient due to the rapid velocity of the gasflow between the moveable substrate and the gas-emanating stationarysupport. Pneumatic levitation is shown to be an effective technology forfilm growth on the moveable substrate from the vapor phase such as isemployed in vapor phase epitaxy. Fluidic levitation wherein a levitationstabilizing structure is employed to positionally stabilize the moveablesubstrate eliminates the complexity of the electronic feedback loops andassociated sensors and equipment, thus simplifying apparatus design.Bernoulli fluidic levitation that employs at least one fluid jet and alevitation stabilizing structure on the moveable substrate is aself-regulating levitation process in which the distance between themoveable substrate and gas-emanating stationary support is determined bya balance between the gravitational force acting on the moveablesubstrate and the fluidic force, either hydraulic or pneumatic, on themoveable substrate that is provided by one or more impinging fluid jets.Additionally, the same fluidic flow that enables self-regulatedflotation of the substrate on a gas cushion also enables control oflateral substrate movement through the interaction of the fluid flow andthe levitation stabilizing structure on the substrate. Thus theself-regulating nature of fluidic levitation can now be used to greatadvantage by employing the invention of the levitation stabilizingstructure during fluidic levitation, thereby allowing the design of newapparatus and associated processes.

It is desirable in some applications that the levitation stabilizingstructure exhibit different chemical reactivity than the substrate uponwhich the levitation stabilizing structure is fabricated. For example,it can be desirable that the levitation stabilizing structure possess aproperty of chemical non-interaction with the process environment towhich said levitation stabilizing structure is exposed. Chemicalinertness of the levitation stabilizing structure is particularly usefulfor certain types of deposition processes to prevent film deposition onthe levitation stabilizing structure thereby aiding the efficiency ofthe removal of the levitation stabilizing structure from the substrateafter processing. For example, there is growing interest in a technologyknown as selective area deposition, or SAD. As the name implies,selective area deposition involves treating portion(s) of a substratesuch that a material is deposited only in those areas that are desired,or selected. Sinha et al. (J. Vac. Sci. Technol. B 24 6 2523-2532(2006)) have remarked that selective area deposition technology asapplied to ALD (Atomic Layer Deposition) requires that designated areasof a surface be masked or “protected” to prevent ALD reactions in thoseselected areas, thus ensuring that the ALD film nucleates and grows onlyon the desired unmasked regions. Sinha et al., used poly(methylmethacrylate (PMMA) in their protective, chemically non-reactive,masking layer. It is also possible to have SAD processes where theselected areas of the surface area are “activated” or surface modifiedin such a way that the film is deposited only on the activated areas.There are many potential advantages to selective area depositiontechniques, particularly to eliminate the necessity of employinglift-off processes for removing the levitation stabilizing structureafter a pneumatically levitated deposition process. Lift off processeshave the disadvantages of unwanted film retention in certain substrateareas and possible redeposition of particulates onto the substrateduring the lift off removal process. The use of selective areadeposition for chemical vapor deposition and atomic layer deposition hasbeen described and is familiar to those skilled in the art. Generally,the use of deposition inhibiting materials comprises providing asubstrate and applying a deposition inhibitor material to saidsubstrate; optionally imagewise patterning the deposition inhibitormaterial; depositing a thin film by chemical vapor deposition or atomiclayer deposition; and optionally removing the deposition inhibitormaterial. The use of deposition inhibitor materials for directeddeposition in different processes has been described in the art,including the use of photosensitive and photopatternable depositioninhibitor materials and many different deposition inhibitor materialsare known in the art. The levitation stabilizing structure itself can befabricated from a deposition inhibiting material directly. In analternative embodiment, the levitation stabilizing structure may have alayer of deposition inhibiting material overlaying and in contact withthe levitation stabilizing structure, the layer of deposition inhibitingmaterial imparting selective area deposition properties onto thelevitation stabilizing structure and modifying the chemical reactivityof said levitation stabilizing structure with respect to depositionprocesses.

U.S. Pat. No. 7,848,644B2 discloses the use of photopatternable layersof siloxane based polymers as director inhibitor compounds for selectivearea deposition.

U.S. Pat. No. 8,153,352 B2 describes a method for fabricating a pixelcircuit comprised of selective deposition employing photopatternableinhibition layers sensitized to specific wavelengths. A multilayered,multicolored mask is prepared on a transparent support which allowsphotopatternable inhibition layers that have been sensitized to respondto specific wavelength of light to be exposed to said wavelength oflight for the purpose of sequentially preparing patterned layers usingpatterned inhibition layers. The photosensitive layers were prepared byadding dyes and sensitizers to a commercially available photoresist(CT2000L from Fuji Photochemicals containing a methacrylate derivativecopolymer and a polyfunctional acrylate resin in a mixture of2-propanol-1-methoxyacetate and 1-ethoxy-2-propanol acetate).

U.S. Pat. No. 8,153,529 B2 describes a method of deposition inhibitionfor atmospheric pressure atomic layer deposition based onphotopatternable layers of hydrophilic polymers wherein the hydrophilicdeposition inhibitor polymer is a hydrophilic polymer that is aneutralized acid having a pKa of 5 of less, wherein at least 90% of theacid groups are neutralized. The advantage of the polymer is the ease ofprocessing with aqueous based solution chemistry. U.S. Pat. No.8,153,529 B2 teaches that the degree of protonation of the depositioninhibition polymer is a potentially important factor determiningdeposition inhibition performance.

U.S. Pat. No. 7,846,644 B2 describes the use of photopatternabledeposition inhibitor films containing siloxane-polymer based materialsfor the purpose of providing a means to pattern films during thedeposition process by inhibiting deposition on regions where thedeposition inhibitor film is present. Siloxane-polymer based materialsare generically defined to include compounds substantially comprising,within their chemical structure, a skeleton or moiety made up ofalternate Si and O atoms, in which at least one, preferably two organicgroups are attached to the Si atom on either side of the —O—Si—O— repeatunits. The organic groups can have various substituents such ashalogens, including fluorine, but most preferably, the organic groupsare independently substituted or unsubstituted alkyl, phenyl, orcycloalkyl groups having 1 to 6 carbon atoms, preferably 1 to 3 carbonatoms, preferably substituted or unsubstituted methyl.

U.S. Pat. No. 8,017,183 B2 describes a process for forming patternedthin films of inorganic materials by applying a patterned layer of anorganosiloxane polymer which may optionally be cross-linked or aphotopatternable polymethyl methacrylate polymer to a substrate followedby atmospheric pressure atomic layer deposition.

U.S. Pat. No. 7,998,878 B2 describes a method for forming patterned thinfilms prepared by atomic layer deposition by applying a depositioninhibitor film to a substrate followed by coating. Numerous types ofdeposition inhibitor films are described with a focus on water solublepolymers. Materials include hydrophilic polymers that are mostlyneutralized as well as other hydrophilic polymers like poly(vinylpyrolidone) based polymers, ethylene oxide based polymers, allylaminebased polymers, and oxazoline based polymers.

U.S. Pat. No. 8,030,212 B2 describes a method for forming patterned thinfilms prepared by atomic layer deposition by applying a depositioninhibitor film to a substrate followed by coating. Numerous types ofdeposition inhibitor films are described and the polymer materialsemployed are mostly soluble in organic solvents. Deposition inhibitorpolymer films include perfluoroalkyl methacrylate polymers, methylmethacrylate polymers, cyclohexyl methacrylate polymers, benzylmethacrylate polymers, isobutylene polymers,9,9-dioctylfluorenyl-2,7-dyl based polymers, polystyrene base polymers,vinyl alcohol based polymers, and hexafluorobutyl methacrylate basedpolymers.

U.S. Pat. No. 8,129,098 B2 describes a process for fabricatingmultilayer patterned structures where the registration between thepatterned layers is optimized through the use of dye sensitizedphotopatternable deposition inhibition layers that have been patternedusing exposure through a multicolored exposure mask. Dye sensitizationof the photopatternable deposition inhibition layers is described. Theuse of several different photopatternable deposition inhibition polymersis described including commercially available methyl methacrylatepolymers and commercially available vinyl terminated methyl siloxanepolymers.

U.S. Pat. No. 8,168,546 B2 describes a method for forming patterned thinfilms prepared by atomic layer deposition by applying a depositioninhibitor film to a substrate followed by coating. Numerous types ofdeposition inhibitor films are described and the polymer materialsemployed are soluble in solutions that are at least 50% by weight water.Preferred deposition inhibitor material is a hydrophilic polymer thathas in its backbone, side chains, or both backbone and side chains,multiple secondary or tertiary amide groups that are represented by thefollowing acetamide structure >N—C(═O)—, where is the hydrophilicpolymer satisfies both of the following tests: a) it is soluble to atleast 1% by weight in a solution containing at least 50 weight % wateras measured at 40° C., and b) it provides an inhibition power of atleast 200 Å to deposition of zinc oxide by an ALD process.

U.S. Pat. No. 8,273,654 describes a method of producing a verticaltransistor comprising: providing a substrate including a gate materiallayer stack with a reentrant profile; depositing an electricallyinsulating material layer over a portion of the gate material layerstack and over a portion of the substrate; depositing a patterneddeposition inhibiting material over the electrically insulating materiallayer; and depositing a semiconductor material layer over theelectrically insulating material layer using a selective area depositionprocess in which the semiconductor material layer is not deposited overthe patterned deposition inhibiting material. The patterned depositioninhibiting material is not specified; however, the methods ofapplication of the deposition inhibiting material taught to includeinkjet printing processes, flexographic printing processes, gravureprinting processes, and photolithographic processes.

U.S. Pat. No. 8,318,249 B2 describes a method for forming a patternedthin film using deposition inhibitor materials in combination withspatial atomic layer deposition comprising: applying a patterneddeposition inhibitor material to a substrate and depositing an inorganicthis film on the substrate spatial atomic layer deposition such that thefilm deposits only in those areas where the deposition inhibitor isabsent where the deposition inhibitor material is a hydrophilicpoly(vinyl alcohol) having a degree of hydrolysis of less than 95%.

U.S. Pat. No. 7,848,644B2, U.S. Pat. No. 8,153,352 B2, U.S. Pat. No.8,153,529 B2, U.S. Pat. No. 7,846,644 B2, U.S. Pat. No. 8,017,183 B2,U.S. Pat. No. 7,998,878 B2, U.S. Pat. No. 8,030,212 B2, U.S. Pat. No.8,129,098 B2, U.S. Pat. No. 8,168,546 B2, U.S. Pat. No. 8,273,654, U.S.Pat. No. 8,318,249 B2 all disclose methods and materials useful forachieving selective area deposition and useful to prevent deposition ona levitation stabilizing structure during a pneumatically levitateddeposition process, the disclosures of which are hereby incorporated byreference in their entirety.

The deposition inhibiting layer can be added to a levitation stabilizingstructure using any method familiar to those skilled in the art ofadditive deposition methods and processes. In one embodiment thedeposition inhibiting layer or deposition inhibiting film can be formedupon a levitation stabilizing structure and moveable support using avapor deposition process. In another embodiment the depositioninhibiting layer or deposition inhibiting film can be formed upon alevitation stabilizing structure and moveable support using a spincoating process. In a third embodiment the deposition inhibiting layeror deposition inhibiting film can be formed upon a levitationstabilizing structure and moveable support using a dip coating process,a spray painting process, a brush painting process, or a stencilingprocess. Other methods of forming or applying a deposition inhibitinglayer to a levitation stabilizing structure and moveable substrate areconceivable and within the scope and spirit of the inventive conceptutilizing the properties of a patterned or unpatterned depositioninhibiting layer in combination with a levitation stabilizing structureon a moveable support. In one embodiment a patterned depositioninhibition layer can be applied to both the moveable substrate and thelevitation stabilizing structure.

The use of deposition inhibiting materials to achieve selectivedeposition on a substrate during, for example, atomic layer depositionis compatible with the use of pneumatic levitation for substrateprocessing as described in this invention. The use of depositioninhibiting materials on a moveable substrate upon which a levitationstabilizing structure has been fabricated is advantageous because rapidgas exchange properties that are inherent to pneumatic levitationprocessing methods leads to short processing times that minimizediffusion of reactive materials through the deposition inhibitingmaterial layers, thereby improving the deposition inhibition andimproving the selectivity of area deposition. Furthermore, it isparticularly advantageous for the levitation stabilizing structure on amoveable substrate to be comprised additionally of one or more layerswhere the outermost and topmost surface of the levitation stabilizingstructure on the movable substrate not in contact with the moveablesubstrate itself has the material properties of a deposition inhibitionmaterial or layer thereby enabling selective area deposition on areasother than the levitation stabilizing structure. A levitationstabilizing structure possessing the property of deposition inhibitionas described in the art is called a deposition inhibiting levitationstabilizing structure. The use of a deposition inhibiting levitationstabilizing structure is especially advantageous when pneumaticlevitation methods in combination with moveable substrates upon which alevitation stabilizing structure has been fabricated are employed inchemical vapor deposition processes or for the purposes of carrying outatomic layer deposition processes.

FIG. 9 shows a moveable substrate 10 with a levitation stabilizingstructure 30 overlaying and in contact with at least one surface ofmoveable substrate 10. The levitation stabilizing structure is comprisedof multiple layers, each layer having a specific function. In oneembodiment shown in FIG. 9 adhesion promoting layer 44 overlaying and incontact with on the substrate is employed to ensure optimal adhesion ofthe entire levitation stabilizing structure 30 to the moveable substrate10. A material layer 46 of a thickness greater than 20 microns isoverlaying and in contact with optional adhesion promoting layer 44.Deposition inhibiting layer 48 is overlaying and in contact withmaterial layer 46 and the exposed portions of the adhesion promotinglayer 44 on the walls of levitation stabilizing structure 30. Depositioninhibiting layer 48 is the outermost layer of the levitation stabilizingstructure 30 and is employed to modify the chemical reactivity of thelevitation stabilizing structure during processing. The outermostdeposition inhibition layer 48 is advantageous for minimizing problemssuch as particle contamination during removal of the levitationstabilizing structure using lift off processes and can be fabricatedfrom any material known in the art to impart deposition inhibitingproperties to a surface. Deposition inhibition layer 48 is overlayingand in contact with material layer 46 and material layer 46 isoverlaying and in contact with optional adhesion promoting layer 44.

Referring to FIG. 10 in an embodiment of the present invention, themoveable substrate 10 has a levitation stabilizing structure 30 andincludes additional structures 31 located within the enclosed interiorimpingement area 35. In one embodiment, the additional structures 31 aresolid; in another embodiment, the additional structures 31 form a closedcurve with its own interior. The additional structures 31 in thelevitation stabilizing structure 30 serve to exclude gas from theportion of the moveable substrate 10 covered by the additionalstructures 31 thereby inhibiting deposition in the covered area, thusallowing the moveable substrate 10 to be provided with patternedthin-film material layers.

Referring to FIGS. 24a-24g in an embodiment of the present invention,the patterning process is illustrated. FIG. 24a illustrates a moveablesubstrate 10. As shown in FIG. 24b , the moveable substrate 10 has alevitation stabilizing structure 30 and includes additional structures31 that are applied to the surface of the moveable substrate 10.Referring to FIG. 24c , a patterned first thin-film layer 51 isdeposited using an embodiment of the present invention to form an atomicthin-film layer whose pattern corresponds to the inverse of theadditional structures 31 in the interior impingement area 35 (notshown). The levitation stabilizing structure 30 is removed and thesubsequent levitation stabilizing structure 30 illustrated in FIG. 24dis applied to the moveable substrate 10 over the first thin-film layer51. The levitation stabilizing structure 30 illustrated in FIG. 24d doesnot include any additional structures 31 so that the subsequent atomiclayer deposition process deposits an unpatterned second thin-film layer52 on the moveable substrate 10 over the first thin-film layer 51 (FIG.24e ). The levitation stabilizing structure 30 is then removed and thesubsequent levitation stabilizing structure 30 with additionalstructures 31 illustrated in FIG. 24f is applied to the moveablesubstrate 10 over the patterned first thin-film layer 51 and theunpatterned second thin-film layer 52. A patterned thin-film layer 53 isdeposited using the atomic layer deposition system of the presentinvention (FIG. 24g ).

In an embodiment, thin-film layers on a common moveable substrate 10 arepatterned using more than one method. For example, thin-film layers arepatterned using the method illustrated in FIGS. 24a-24g and using themethod of deposition inhibition, as described below. Single layers canbe patterned using both techniques together or sequential layers can bealternately patterned using first one method and then another.

In another embodiment the entire levitation stabilizing structure can befabricated from a material possessing deposition inhibition properties.In this embodiment the material layer 46 of FIG. 9 has the property ofenabling selective area deposition, thereby eliminating the need for aseparate deposition inhibiting layer 48.

Deposition inhibition materials employed for selective area depositionduring deposition process such as but not restricted to atomic layerdeposition are typically thin and provide a distinct advantage when sucha layer or layer properties are applied to levitation stabilizingstructure because the layer can potentially aid in post-processing ofthe levitation stabilizing structure. For example, when the surface ofthe levitation stabilizing structure on a moveable substrate has theproperty of deposition inhibition, then the deposited material from thedeposition process like, for example, an oxide film deposited by atomiclayer deposition will not be present on the regions having thedeposition inhibition material property. The regions where the depositedmaterial is absent will, therefore, be easier to remove in subsequentpost-deposition processing if desired. It will be clear to those skilledin the art of post-deposition processing that such processes like, forexample, lift-off processes that are commonly used in combination withpatterned resists will not be necessary. This is desirable becausepost-deposition processing steps such as lift-off processes can lead toparticle contamination, thereby reducing yield and product quality.

Furthermore, it is advantageous to use a moveable substrate with adeposition inhibiting levitation stabilizing structure duringpneumatically levitated atomic layer deposition processing incombination with a patterned deposition inhibition layer on the moveablesubstrate itself for the purpose of selective deposition of a thin filmin the regions on the surface of the moveable substrate where thedeposition inhibition layer is absent. The levitation stabilizingstructure, with or without deposition inhibiting properties, allows theuse of deposition inhibiting materials on a moveable substrate in apneumatically levitated deposition process without the use of physicalstops to stabilize the substrate position during pneumatic levitation.

The inventive method of fluidic levitation stabilization using alevitation stabilizing structure in contact with and overlaying at leastone surface of a moveable substrate will be further understood byreference to the examples below wherein the inventive method is employedto achieve fluidic levitation of plate-like substrates.

Examples 1-14: Pneumatic Levitation with and without LevitationStabilizing Structures

The purpose of the following examples is to demonstrate theeffectiveness of levitation stabilizing structures for improving thepositional stability of pneumatically levitated moveable substrates.Recalling that all prior art employed physical stops on thegas-emanating stationary support in order to prevent undesirablemoveable substrate motion that would cause failure of pneumaticlevitation, note that examples 1-14 were carried out in the absence ofany physical stops being present on the gas-emanating stationary supportthat could impede moveable substrate motion. In other words, since themotion of the moveable substrate was completely unimpeded duringpneumatic levitation, failure of the sample to remain in a stableposition during pneumatic levitation could be easily detected, therebyenabling a simple determination of moveable substrate configurationswhich are positionally stable during pneumatic levitation.

In examples 1-14 the stationary support through which fluid will flowwas comprised of a block of nylon having dimensions of 8″×8″×1″ with a 4mm diameter orifice in the center of the 8″×8″ surface. The 4 mmdiameter orifice in the stationary support through which fluid will flowwas machined so that it produces a gaseous jet from the gas emanatingsurface of the stationary support that is normal or orthogonal to thesurface of the stationary support. During experimentation the moveablesubstrate was place on the support with one surface opposing thestationary gaseous emitting surface through which fluid will flow suchthat the orthogonal jet produced by the fluid collimating conduit in thegas emanating stationary support was also orthogonal to the opposingsurface of the moveable substrate as illustrated in FIG. 4. The 4 mmfluid collimating conduit of the stationary support was in fluid contactwith a manifold to which was equipped with a pressure gauge and a massflow meter and the manifold was, in turn, in fluid contact with a sourceof pressurized gaseous fluid. The pressurized gaseous fluid wascontrolled using a valve and a pressure regulator. Pressurized air wasused as the gaseous fluid for the production of orthogonal jets in allexperiments. The pressure of the gaseous fluid was measured duringexperiments using a digital pressure gauge (Cecomp model DPG1000L100psig) and the gaseous flow was measured using a mass flow meter(Mattheson model 8112-0444 calibrated for air). Sample height before andduring pneumatic levitation was measured optically. A video camera(Watek model WAT 902H Ultimate) coupled to a lens assembly (NavitarCorp.) that was focused at the contact point between the moveablesubstrate to the nylon block and a fiber optic light source was placedsuch that when the sample was not levitated by pneumatic levitationthere was no light to the camera because it was blocked by thesubstrate; similarly when the substrate underwent pneumatic levitationthere was light transmitted through the gap between the moveablesubstrate and the stationary support containing the orthogonal jet,thereby enabling optical measurement of the displacement of the moveablesubstrate as a result of pneumatic levitation. Positional stability ofthe moveable substrate during pneumatic levitation was assessed byvisual observation of the lateral displacement of the moveable substratein directions parallel to the stationary support gas emanating surface.When a moveable substrate was not positionally stable during pneumaticlevitation it was found that the moveable substrate would undergolateral displacements that forced the moveable substrate completely offthe surface of the gas emanating stationary support as described in U.S.Pat. No. 3,466,079. Moveable substrates in various configurations wereconsidered positionally stable if the moveable substrate showed nomotion of any type during when pneumatically levitated or if themoveable substrate showed stable rotation or oscillatory motion over atime period of several minutes around a rotational axis or oscillationcenter that was coincident with the orthogonal jet produced by the flowof gaseous fluid from the gas emanating surface of the stationarysupport.

All levitation stabilizing structures on the moveable substrates werefabricated using conventional methods familiar to those skilled in theart of photolithography. In examples 1-6, 10, and 12 a levitationstabilizing structure was fabricated upon one surface of silicon wafer.Silicon wafers with a diameter of 150 mm and a thickness of 675 micronswere employed as silicon wafer substrates. The photoresist used here wasa negative photoresist (MicroChem SU8 2050) and the photoresist wasdeveloped using a Laurell Technologies spin coater. The exposure maskswere prepared using transparencies. All wafers were cleaned by immersionin a 60° C. EKC-256 bath for 10 minutes followed by a spin-rinse-drycycle. Some wafers were optionally pretreated with an adhesion promotinglayer of HMDS to aid adhesion of the photoresist to the wafer surfaceduring processing. The resist was manually dispensed onto the waferusing a spin coater (Mark V Tel Track) using the following procedure: 1)5-7 grams of SU8-2050 photoresist was dispensed onto the wafer for 3seconds at 50 psi 2) the wafer was spun at 1000 rpm for 60 secondsfollowed by edge bead removal 3) the wafer was baked in a two-stepprocess at 65° C. for 4 minutes followed by a second bake at 95° C. for4 minutes. Steps 1-3 were repeated until a resist thickness ofapproximately 200±10 microns was coated on the wafer. The resist wasexposed through the transparency mask using a Karl Suss MA6 exposuretool using an I-line light source with a strong emission at 365 nm.After exposure, the wafers were baked for 10 minutes at 95° C. Thephotoresist layer on the wafer was developed using a LaurellTechnologies spin coater with apropylene-glycol-mono-methyl-ether-acetate (PGMEA) developer. The PGMEAdeveloper was applied using 8-10 puddles with a 60 sec exposure for eachpuddle. The PGMEA resist development was followed by an isopropylalcohol rinse for 2 min while spinning at 200 rpm. The wafers were thenspun dry using nitrogen for 2 minutes at 2000 rpm. Thus, the levitationstabilizing structure was fabricated on the surface of a moveablesubstrate—a silicon wafer—using SU8 photoresist with conventionalphotolithographic methods. It is recognized that other photoresists andphotofabrication methods familiar to those skilled in the art ofphotofabrication can be used to prepare levitation stabilizingstructures on the surface of moveable substrates and that it is notrequired that the substrate be substantially flat and planar.

Example 1

2000 Å of thermal oxide was grown on a 675 micron thick, 150 mm diametersilicon wafer with a flat to indicate wafer orientation. The surface ofwafer was completely featureless and planar. The wafer of example 1 wasmounted on the stationary gas emitting support and an attempt was madeto pneumatically levitate the moveable substrate at orthogonal jetmanifold pressures between 10 and 35 psig. Although the wafer substratelevitated, the pneumatic levitation was not positionally stable andexhibited excessive, rapidly developing lateral motion. The moveablesubstrate of example 1 rapidly slid off the surface of the stationarygas emitting support: it did not remain in stationary during pneumaticlevitation. Example 1 failed pneumatic levitation testing due toinsufficient positional stability during levitation.

Example 2

A levitation stabilizing structure consisting of an annulus having 100mm inside diameter, 102 mm outside diameter, and a height ofapproximately 200 microns was fabricated on the surface of a 650 micronthick, 150 mm diameter silicon wafer with a flat that indicated waferorientation. The levitation stabilizing structure was fabricated bycoating the wafer with SU-8 resist that was photolithographicallypatterned and developed to produce the levitation stabilizing structureon the surface of the moveable wafer substrate of example 2. The surfaceof the wafer was completely featureless and planar with the exception ofthe levitation stabilizing structure. The wafer of example 2 was mountedon the stationary gas emitting support and an attempt was made topneumatically levitate the moveable substrate at manifold pressuresbetween 10 and 35 psig. The moveable substrate of example 2 waspneumatically levitated at orthogonal jet manifold pressures greaterthan 10 psig and showed excellent positional stability at 30 psig,giving a pneumatic levitation height of 200 microns. The moveablesubstrate with levitation stabilizing structure could be disturbedeither by physically pushing the moveable substrate of example 2 duringpneumatic levitation or by using an air stream to push the samplearound. When disturbed, the moveable substrate of example 2 with alevitation stabilizing structure went into oscillations and after aperiod of time returned to a stable position with minimal movementduring pneumatic levitation. Example 2 passed pneumatic levitationtesting and demonstrated excellent positional stability duringlevitation.

Example 3

A 650 micron thick, 150 mm diameter silicon wafer with a flat toindicate wafer orientation onto with a levitation stabilizing structureconsisting of an annulus having 125 mm inside diameter, 127 mm outsidediameter, and a height of approximately 200 microns. The levitationstabilizing structure was fabricated by coating the wafer with SU-8resist that was photolithographically patterned and developed to producethe levitation stabilizing structure on the surface of the moveablewafer substrate of example 3. The surface of the wafer was completelyfeatureless and planar with the exception of the levitation stabilizingstructure. The wafer with levitation stabilizing structure of example 3was mounted on the stationary gas emitting support and an attempt wasmade to pneumatically levitate the moveable substrate at manifoldpressures between 10 and 35 psig. The moveable substrate of example 3was pneumatically levitated at orthogonal jet manifold pressures greaterthan 10 psig and showed excellent positional stability at 20 psig,giving a pneumatic levitation height of 200 microns. The moveable samplewith levitation stabilizing structure could be disturbed either byphysically pushing the moveable substrate of example 3 during pneumaticlevitation or by using an air stream to push the sample around. Whendisturbed, the moveable substrate of example 3 with a levitationstabilizing structure went into oscillations and after a period of timereturned to a stable position with minimal movement during pneumaticlevitation. Example 3 passed pneumatic levitation testing anddemonstrated excellent positional stability during levitation.

Example 4

A 650 micron thick, 150 mm diameter silicon wafer with a flat toindicate wafer orientation with a levitation stabilizing structureconsisting of an annulus having 135 mm inside diameter, 137 mm outsidediameter, and a height of approximately 200 microns. The levitationstabilizing structure was fabricated by coating the wafer with SU-8resist that was photolithographically patterned and developed to producethe levitation stabilizing structure on the surface of the moveablewafer substrate of example 4. The surface of the wafer was completelyfeatureless and planar with the exception of the levitation stabilizingstructure. The wafer of example 4 was mounted on the stationary gasemitting support and an attempt was made to pneumatically levitate themoveable substrate at manifold pressures between 10 and 35 psig. Themoveable substrate of example 4 was pneumatically levitated atorthogonal jet manifold pressures greater than 10 psig and showedexcellent positional stability at 20 psig, giving a pneumatic levitationheight of 150 microns. The moveable sample with levitation stabilizingstructure could be disturbed either by physically pushing the moveablesubstrate of example 3 during pneumatic levitation or by using an airstream to push the sample around. When disturbed, the moveable substrateof example 4 with a levitation stabilizing structure went intooscillations and after a period of time returned to a stable positionwith minimal movement during pneumatic levitation. Example 4 passedpneumatic levitation testing and demonstrated excellent positionalstability during levitation.

Example 5

A 650 micron thick, 150 mm diameter silicon wafer with a flat toindicate wafer orientation with a levitation stabilizing structureconsisting of a square having 98 mm inside diameter, 100 mm outsidediameter, and a height of approximately 200 microns. The levitationstabilizing structure was fabricated by coating the wafer with SU-8resist that was photolithographically patterned and developed to producethe levitation stabilizing structure on the surface of the moveablewafer substrate of example 5. The surface of the wafer was completelyfeatureless and planar with the exception of the square shapedlevitation stabilizing structure. The wafer of example 5 was mounted onthe stationary gas emitting support and an attempt was made topneumatically levitate the moveable substrate at manifold pressuresbetween 10 and 35 psig. The moveable substrate of example 5 waspneumatically levitated at orthogonal jet manifold pressures greaterthan 10 psig and showed excellent positional stability between 20 and 30psig, giving pneumatic levitation heights of 330±20 and 250±20 microns,respectively. The moveable sample with levitation stabilizing structurecould be disturbed either by physically pushing the moveable substrateof example 5 during pneumatic levitation or by using an air stream topush the sample around. When disturbed, the moveable substrate ofexample 5 with a levitation stabilizing structure went into rotationwith additional lateral pendulum-like oscillations and after a period oftime returned to a stable position with minimal movement duringpneumatic levitation. Example 5 passed pneumatic levitation testing anddemonstrated excellent positional stability during levitation.

Example 6

A 650 micron thick, 150 mm diameter silicon wafer with a flat toindicate wafer orientation with a levitation stabilizing structureconsisting of a rectangle having 73 mm×98 mm inside dimensions, 75mm×100 mm outside dimensions, and a height of approximately 200 microns.The levitation stabilizing structure was fabricated by coating the waferwith SU-8 resist that was photolithographically patterned and developedto produce the levitation stabilizing structure on the surface of themoveable wafer substrate of example 6. The surface of the wafer wascompletely featureless and planar with the exception of the rectangularlevitation stabilizing structure. The wafer of example 6 was mounted onthe stationary gas emitting support and an attempt was made topneumatically levitate the moveable substrate at manifold pressuresbetween 10 and 35 psig. The moveable substrate of example 6 waspneumatically levitated at orthogonal jet manifold pressures greaterthan 10 psig and showed excellent positional stability between 20 and 30psig, giving pneumatic levitation heights of 350±20 and 250±20 microns,respectively. The moveable sample with levitation stabilizing structurecould be disturbed either by physically pushing the moveable substrateof example 6 during pneumatic levitation or by using an air stream topush the sample around. When disturbed, the moveable substrate ofexample 6 with a levitation stabilizing structure went into rotationwith additional horizontal pendulum like oscillations and after a periodof time returned to a stable position with minimal rotational movementduring pneumatic levitation. Example 6 passed pneumatic levitationtesting and demonstrated excellent positional stability duringlevitation.

Example 7

The moveable substrate of example 7 consisted of 90 mm diameterpolystyrene petri dish prepared by injection molding. The mold used forinjection molding included an 89 mm outside diameter rim or annulusintegrated into the dish made of polystyrene and formed at the same timeas the petri dish itself. The rim on the bottom of the dish wasapproximately 600 microns wide and approximately 250 microns in height.Thus, the bottom of the petri dish was equipped with an integratedlevitation stabilizing structure that was tested for efficacy. The petridish of example 7 was mounted on the stationary gas emitting supportwith the 89 mm outside diameter 250 micron high rim opposing thestationary gas emitting support such that the remaining surface of thebottom of the dish was opposing the gas emitting 4 mm fluid collimatingconduit contained in the stationary gas emitting support and an attemptwas made to pneumatically levitate the moveable substrate at manifoldpressures between 1 and 30 psig. The moveable substrate of example 7 waspneumatically levitated at orthogonal jet manifold pressures greaterthan 3 psig and showed excellent positional stability at 4.2 psi, givinga pneumatic levitation height of 135±30 microns. The moveable samplewith levitation stabilizing structure could be disturbed either byphysically pushing the moveable substrate of example 7 during pneumaticlevitation or by using an air stream to push the sample around. Whendisturbed, the moveable substrate of example 7 with a levitationstabilizing structure went into oscillations and after a period of timereturned to a stable position with minimal rotational movement duringpneumatic levitation. Example 7 passed pneumatic levitation testing anddemonstrated excellent positional stability during levitation.

Example 8

The moveable substrate of example 8 consisted of 90 mm diameterpolystyrene petri dish prepared by injection molding. The mold used forinjection molding included a 89 mm outside diameter rim or annulusintegrated into the dish made of polystyrene and formed at the same timeas the petri dish itself. The rim on the bottom of the dish wasapproximately 600 microns wide and approximately 600 microns in height.Thus, the bottom of the petri dish was equipped with an integratedlevitation stabilizing structure that was tested for efficacy. The petridish of example 8 was mounted on the stationary gas emitting supportwith the 89 mm outside diameter 600 micron high rim opposing thestationary gas emitting support such that the remaining surface of thebottom of the dish was opposing the gas emitting 4 mm fluid collimatingconduit contained in the stationary gas emitting support and an attemptwas made to pneumatically levitate the moveable substrate at manifoldpressures between 1 and 30 psig. The moveable substrate of example 8 waspneumatically levitated at orthogonal jet manifold pressures greaterthan 1 psig and showed excellent positional stability at 1.8 and 10 psi,giving pneumatic levitation heights of 300±30 and 250±30 microns,respectively. The moveable sample with levitation stabilizing structurecould be disturbed either by physically pushing the moveable substrateof example 8 during pneumatic levitation or by using an air stream topush the sample around. When disturbed, the moveable substrate ofexample 8 with a levitation stabilizing structure went into oscillationsand after a period of time returned to a stable position with minimalrotational movement during pneumatic levitation. Example 8 passedpneumatic levitation testing and demonstrated excellent positionalstability during levitation.

Example 9

The moveable substrate of example 9 consisted of 92 mm diameterpolystyrene petri dish prepared by injection molding. The mold used forinjection molding included a 90 mm outside diameter rim or annulusintegrated into the dish made of polystyrene and formed at the same timeas the petri dish itself. The rim on the bottom of the dish wasapproximately 600 microns wide and approximately 130 microns in height.Thus, the bottom of the petri dish was equipped with an integratedlevitation stabilizing structure that was tested for efficacy. The petridish of example 9 was mounted on the stationary gas emitting supportwith the 90 mm outside diameter 130 micron high rim opposing thestationary gas emitting support such that the remaining surface of thebottom of the dish was opposing the gas emitting 4 mm fluid collimatingconduit contained in the stationary gas emitting support and an attemptwas made to pneumatically levitate the moveable substrate at manifoldpressures between 1 and 10 psig. The moveable substrate of example 9 waspneumatically levitated at orthogonal jet manifold pressures greaterthan 3 psig and showed excellent positional stability at 3.2 and 5 psi,giving pneumatic levitation heights of 130±30 and 90±30 microns,respectively. The moveable sample with levitation stabilizing structurecould be disturbed either by physically pushing the moveable substrateof example 9 during pneumatic levitation or by using an air stream topush the sample around. When disturbed, the moveable substrate ofexample 9 with a levitation stabilizing structure went into oscillationsand after a period of time returned to a stable position with minimalrotational movement during pneumatic levitation. Example 9 passedpneumatic levitation testing and demonstrated good positional stabilityduring levitation.

Example 10

The moveable substrate of example 5 was modified by using a dicing sawto trim the roughly circular shape of the moveable silicon substrate toa square shape that roughly matched the dimensions of the levitationstabilizing structure already on the moveable substrate. The outsidedimensions of the diced moveable substrate were 105 mm×105 mm. Thepurpose of this example is to demonstrate that the levitationstabilization structure functions regardless of substrate shape andallows pneumatic levitation of arbitrarily shaped moveable substrates.The square moveable substrate with a square levitation stabilizingstructure of example 10 was mounted on the stationary gas emittingsupport with the levitation stabilizing structure opposing thestationary gas emitting support such that the surface of the moveablesubstrate was opposing the gas emitting 4 mm fluid collimating conduitcontained in the stationary gas emitting support and an attempt was madeto pneumatically levitate the moveable substrate at manifold pressuresbetween 1 and 35 psig. The moveable substrate of example 10 waspneumatically levitated at orthogonal jet manifold pressures greaterthan 5 psig and showed excellent positional stability at 16 psi, givingpneumatic levitation heights of 500±50 microns. The moveable sample withlevitation stabilizing structure could be disturbed either by physicallypushing the moveable substrate of example 10 during pneumatic levitationor by using an air stream to push the sample around. When disturbed, themoveable substrate of example 10 with a levitation stabilizing structurewent into oscillations and after a period of time returned to a stableposition with minimal rotational movement during pneumatic levitation.Example 10 passed pneumatic levitation testing and demonstrated goodpositional stability during levitation and demonstrates the applicationof a levitation stabilizing structure to essentially planar moveablesubstrates of arbitrary shape.

Example 11

A 650 micron thick, 150 mm diameter silicon wafer with a flat toindicate wafer orientation and having only native oxide on the moveablesubstrate surface was diced to a square shape having dimensions of 105mm×105 mm that was identical to the moveable substrate dimensions ofexample 10. One of the surfaces of the wafer was completely featurelessand planar and the other side was covered with CMOS type circuits (anexample of a structured surface). The wafer of example 11 was mounted onthe stationary gas emitting support and an attempt was made topneumatically levitate the moveable substrate at orthogonal jet manifoldpressures between 1 and 35 psig. Although the wafer substrate levitated,the pneumatic levitation was not positionally stable and exhibitedpronounced rapid lateral motion during pneumatic levitation. Themoveable substrate of example 11 rapidly slid off the surface of thestationary gas emitting support: it did not remain in stationary duringpneumatic levitation regardless of which side was opposing theorthogonal jet. The experiment was repeated on both sides of thesubstrate with the same results. Example 11 failed pneumatic levitationtesting due to insufficient positional stability during levitation,thereby demonstrating that the stable pneumatic levitation observed inprevious examples was not related to the square shape of the substrate,or the presence or absence of additional surface topography on themoveable substrate but is instead attributed to the presence of alevitation stabilizing structure on the moveable substrate surface.

Example 12

The purpose of this example is to demonstrate that the levitationstabilization structure functions regardless of substrate shape andallows pneumatic levitation of arbitrarily shaped moveable substrates.The moveable substrate of example 6 was modified by using a dicing sawto trim the roughly circular shape of the moveable silicon substrate toa rectangular shape that roughly matched the dimensions of thelevitation stabilizing structure already on the moveable substrate. Theoutside dimensions of the diced moveable substrate were 105 mm×80 mm.The rectangular moveable substrate with a rectangular levitationstabilizing structure of example 12 was mounted on the stationary gasemitting support with the levitation stabilizing structure opposing thestationary gas emitting support such that the surface of the moveablesubstrate was opposing the gas emitting 4 mm fluid collimating conduitcontained in the stationary gas emitting support and an attempt was madeto pneumatically levitate the moveable substrate at manifold pressuresbetween 1 and 35 psig. The moveable substrate of example 12 waspneumatically levitated at orthogonal jet manifold pressures greaterthan 5 psig and showed excellent positional stability at 7-8 psi. Themoveable sample with levitation stabilizing structure could be disturbedeither by physically pushing the moveable substrate of example 12 duringpneumatic levitation or by using an air stream to push the samplearound. When disturbed, the moveable substrate of example 12 with alevitation stabilizing structure went into oscillations and after aperiod of time returned to a stable position with minimal rotationalmovement during pneumatic levitation. Example 12 passed pneumaticlevitation testing and demonstrated good positional stability duringlevitation and demonstrates the application of a levitation stabilizingstructure to essentially planar moveable substrates of arbitrary shape.

Example 13

A 650 micron thick, 150 mm diameter silicon wafer with a flat toindicate wafer orientation on the moveable substrate surface was dicedto a rectangular shape having dimensions of 105 mm×80 mm that wasidentical with the moveable substrate dimensions of example 12. One ofthe surfaces of the wafer was completely featureless and planar and theother side was covered with CMOS type circuits (an example of astructured surface). The wafer of example 13 was mounted on thestationary gas emitting support and an attempt was made to pneumaticallylevitate the moveable substrate at orthogonal jet manifold pressuresbetween 1 and 35 psig. Although the wafer substrate levitated, thepneumatic levitation was not positionally stable and the moveablesubstrate of example 13 rapidly slid off the surface of the stationarygas emitting support with a rapid lateral motion: it did not remain instationary during pneumatic levitation. The experiment was repeated onboth sides of the substrate with the same results. Example 13 failedpneumatic levitation testing due to insufficient positional stabilityduring levitation, thereby demonstrating that the stable pneumaticlevitation observed in examples 13 was not related to the rectangularshape of the substrate, or the presence or absence of additional surfacetopography on the moveable substrate but rather to the presence of alevitation stabilizing structure on the surface of the moveablesubstrate of arbitrary shape.

Example 14

A 650 micron thick, 150 mm diameter silicon wafer with a flat toindicate wafer orientation and having only native oxide on the moveablesubstrate surface was cleaned in a heated bath of EKC-256 at 60 degreesC. followed by a high purity water rinse and a spin dry cycle. Twolayers of 120 micron thick WBR2000 thick film resist were laminated ontothe surface of the wafer using a lamination roll pressure of 1.7 kPa at95 degrees C. and a roll speed of 1.2 meter/min. The photoresist wasexposed for a 100 seconds to I line radiation (365 nm) through a maskafter which the photoresist was developed with 1.2% by volume DX40developer for 35 minutes. Following development the wafer was rinsedwith high purity water and spun dry. The surface of the wafer wascompletely featureless and planar with the exception of the annularlevitation stabilizing structure with a 128 mm ID and a 130 mm ODprotruding approximately 230 microns from the substrate surface. Therewere some wrinkles and defects in the laminated structure that protrudedfurther than 230 microns from the substrate surface. The wafer ofexample 14 was mounted on the stationary gas emitting support and anattempt was made to pneumatically levitate the moveable substrate atmanifold pressures between 10 and 35 psig. The moveable substrate ofexample 14 was pneumatically levitated at orthogonal jet manifoldpressures greater than 10 psig and showed excellent positional stabilityaround 20 psig, giving a pneumatic levitation height of 350±20 microns.The moveable sample with levitation stabilizing structure could bedisturbed either by physically pushing the moveable substrate of example14 during pneumatic levitation or by using an air stream to push thesample around. When disturbed, the moveable substrate of example 14 witha levitation stabilizing structure went into rotation with additionalhorizontal pendulum like oscillations and after a period of timereturned to a stable position with minimal movement during pneumaticlevitation. Example 14 passed pneumatic levitation testing anddemonstrated excellent positional stability during levitation. Removalof patterned and developed WBR 2000 film was accomplished using EKC265followed by O2 plasma cleaning for 1 hour at 900 Watts plasma power. Thelevitation stabilizing structure comprised of developed WBR2000 resistwas removed from the surface of the silicon wafer substrate anddefectivity measurements taken using light scattering indicated that theresist was completely removed and substrate was sufficiently clean sothat it could be used in subsequent processing operations.

Example 15

A 380 micron thick, 150 mm diameter silicon wafer with a flat toindicate wafer orientation and having surface topography in the form ofCMOS circuitry on one side and a plurality of through vias extendingfrom the front side containing the CMOS circuitry to the backside of thewafer so that the front and the backside of the wafer are in fluidcommunication using the through vias was cleaned in a heated bath ofEKC-256 at 60 degrees C. followed by a high purity water rinse and aspin dry cycle. Two layers of 120 micron thick WBR2000 thick film resistwere laminated onto the surface of the wafer with CMOS circuitry using alamination roll pressure of 1.7 kPa at 95 degrees C. and a roll speed of1.2 meter/min. The photoresist was exposed for a 100 seconds to I lineradiation (365 nm) through a mask after which the photoresist wasdeveloped with 1.2% by volume DX40 developer for 35 minutes. Followingdevelopment the wafer was rinsed with high purity water and spun dry.The front surface of the wafer had CMOS circuits and a annularlevitation stabilizing structure thereupon, the dimensions of theannular levitation stabilizing structure being 134 mm ID, 136 mm OD,with a height of approximately 240 microns. Thus the annular levitationstabilizing structure was positioned on top of the CMOS circuits on thesubstrate surface and extended approximately 240 microns from the CMOScircuit surface. There were some wrinkles and defects in the laminatedstructure that protruded further than 240 microns from the substratesurface. The wafer of example 15 was mounted on the stationary gasemitting support and an attempt was made to pneumatically levitate themoveable substrate at manifold pressures between 10 and 35 psig. Themoveable substrate of example 15 was pneumatically levitated atorthogonal jet manifold pressures greater than 10 psig and showedexcellent positional stability around 20 psig, giving a pneumaticlevitation height of 350±20 microns. The moveable sample with levitationstabilizing structure could be disturbed either by physically pushingthe moveable substrate of example 14 during pneumatic levitation or byusing an air stream to push the sample around. When disturbed, themoveable substrate of example 15 with a levitation stabilizing structurewent into rotation with additional horizontal pendulum like oscillationsand after a period of time returned to a stable position with minimalmovement during pneumatic levitation. Example 15 passed pneumaticlevitation testing and demonstrated excellent positional stabilityduring levitation, demonstrating that the positional stability achievedwith a levitation stabilizing structure during pneumatic levitation withan orthogonal fluid jet is applicable to thinned wafers and,unexpectedly, can also stabilizing the pneumatic levitation of waferscontaining a plurality of holes as well as wafers with surfacetopography.

Example 16

A 650 micron thick, 150 mm diameter silicon wafer with a flat toindicate wafer orientation and having surface topography in the form ofCMOS circuitry on one side on the moveable substrate surface was cleanedin a heated bath of EKC-256 at 60 degrees C. followed by a high puritywater rinse and a spin dry cycle. Three layers of 120 micron thickWBR2000 thick film resist were laminated onto the surface of the waferusing a lamination roll pressure of 1.7 kPa at 95 degrees C. and a rollspeed of 1.2 meter/min. The photoresist was exposed to I line radiation(365 nm) through a mask after which the photoresist was developed with1.2% by volume DX40 developer for 35 minutes. Following development thewafer was rinsed with high purity water and spun dry. The surface of thewafer was topographically complex with an annular levitation stabilizingstructure positioned thereupon, the annular levitation stabilizingstructure with a 134 mm ID and a 136 mm OD protruding approximately 360microns from the substrate surface. The wafer of example 16 was mountedon the stationary gas emitting support with the levitation stabilizingstructure facing the stationary gas emitting support and an attempt wasmade to pneumatically levitate the moveable substrate at manifoldpressures between 10 and 35 psig. The moveable substrate of example 14was pneumatically levitated at orthogonal jet manifold pressures greaterthan 10 psig and showed excellent positional stability around 13.5 psig,giving a pneumatic levitation height of 500±20 microns. The moveablesample with levitation stabilizing structure could be disturbed eitherby physically pushing the moveable substrate of example 16 duringpneumatic levitation or by using an air stream to push the samplearound. When disturbed, the moveable substrate of example 16 with alevitation stabilizing structure went into rotation with additionalhorizontal pendulum like oscillations and after a period of timereturned to a stable position with minimal movement during pneumaticlevitation. Example 16 passed pneumatic levitation testing anddemonstrated excellent positional stability during levitation of asubstrate with complex topographical features associated with CMOScircuitry.

The results of examples 1 through 16 are summarized in Table 1 below.

Pneumatic Substrate LSS levitation test Example # shape (Yes/No) LSSshape (Pass/Fail) 1 Circular No Fail 2 Circular Yes Circular Pass 3Circular Yes Circular Pass 4 Circular Yes Circular Pass 5 Circular YesSquare Pass 6 Circular Yes Rectangular Pass 7 Circular Yes Circular Pass8 Circular Yes Circular Pass 9 Circular Yes Circular Pass 10 Square YesSquare Pass 11 Square No Fail 12 Rectangular Yes Rectangular Pass 13Rectangular No Fail 14 Circular Yes Circular Pass 15 Circular YesCircular Pass 16 Circular Yes Circular Pass

The results that are summarized in Table 1 demonstrate that samples withlevitation stabilizing structures on their surfaces according to theinvention exhibit stable pneumatic levitation independent of substrateshape or polygonal shape of the levitation stabilizing structure.

Levitation Apparatus

Another embodiment of the present invention provides an apparatus forfluidic levitation of a moveable substrate with a levitation stabilizingstructure using spatially and compositionally ordered fluids of variedcomposition wherein the composition of the spatially ordered andcompositionally ordered fluid can be varied as desired for the purposesof fluidic levitation and fluidic levitation applications. Theadvantages of substrate processing by fluidic levitation methods havebeen previously enumerated.

In particular, the invention provides a non-contact method for achievingpositional stability of a substrate during fluid levitation wherein thelateral motion of a planar substrate is controlled during fluidlevitation and the fluid is a gas or a liquid and the fluid contains areactive chemical. Another embodiment provides a non-contact method forachieving positional stability of a substrate during fluid levitationwherein the lateral motion of a planar polygonal shaped substrates iscontrolled during fluidic levitation and the fluid is a gas or a liquid.Other embodiments provide a non-contact method for achieving positionalstability of a pneumatically levitated substrate floating on achemically reactive gaseous fluid layer produced by a collimatedreactive fluid gaseous jet during substrate processing for the purposeof reducing the substrate defectivity incurred as a result ofprocessing.

A further embodiment provides a non-contact method of achievingpositional stability of a substrate levitated hydraulically orpneumatically on a fluid layer produced by a chemically reactive fluidjet wherein the method is compatible with miniaturization for thepurpose of integrating said method of positional stabilization of asubstrate during fluidic levitation into microelectromechanical systemsfor the purpose of producing novel and hitherto unknown miniaturizedfluidic, pneumatic, or hydraulic devices as well as novelmicromechanical and micro-fluidic devices operating with liquids orgases. The invention also provides a method for utilizing andcontrolling fluid energy and reactive fluid flow on a miniature ormicroscopic scale by either passive or active means.

Alternatively, the invention provides a method for producing fluid flowscontaining chemically reactive substances for the purpose of substrateprocessing during fluidic levitation of a substrate wherein the fluid iseither a gas or a liquid and the fluid exhibits minimal chemicalinteraction with the fluid delivery system employed in the fluidiclevitation process. As such, the invention provides an apparatus forproducing fluid flows containing chemically reactive substances for thepurpose of substrate processing during fluidic levitation of a substratewherein the fluid thereby produced exhibits minimal chemical interactionwith the fluid delivery system employed in the fluidic levitationprocess.

In another embodiment, the invention provides a non-contact method forachieving stable fluidic levitation of a substrate with a fluid flowwherein the fluid is either a gas or a liquid, said fluid beingchemically reactive. The invention also provides a non-contact methodfor achieving stable fluidic levitation of a substrate with a fluid flowwherein the fluid is either a gas or a liquid, said fluid beingchemically reactive and exposing at least one surface of the levitatingsubstrate to the chemically reactive substances in the chemicallyreactive fluid flow.

Another embodiment of the invention provides a method for producingcompositionally segregated fluid flows for the purpose of fluidiclevitation of a substrate wherein the fluid is either a gas or a liquid.An objective of the invention is to provide an apparatus for producingcompositionally segregated fluid flows for the purpose of fluidiclevitation of a substrate.

Another embodiment of the invention provides a method of fluidiclevitation that employs fluids having a non-uniform composition ofmatter. Another objective of the invention is to provide an apparatusfor production of a fluid having a non-uniform composition of matterduring a fluidic levitation process.

Another embodiment of the invention provides a method for producingcompositionally segregated fluid flows for the purpose of substrateprocessing during fluidic levitation of a substrate wherein the fluid iseither a gas or a liquid. An objective of the invention is to provide anapparatus for producing compositionally segregated fluid flows for thepurpose of substrate processing during fluidic levitation of asubstrate. It is an objective of the invention to provide an apparatusfor generating and creating spatially and compositionally ordered fluidsof varied composition wherein the composition of the spatially orderedand compositionally ordered fluid can be varied as desired for thepurposes of fluidic levitation and fluidic levitation applications, saidfluid being either a liquid or a gas.

Another embodiment of the invention provides a method for producingcompositionally segregated fluid flows with at least one chemicallyreactive compositionally segregated region for the purpose of fluidiclevitation of a substrate wherein the fluid is either a gas or a liquid.An objective of the invention is to provide an apparatus for producingcompositionally segregated fluid flows with at least one chemicallyreactive compositionally segregated region for the purpose of fluidiclevitation of a substrate.

Another embodiment of the invention provides a method of dosing orexposing a substrate surface to a reactive flow for a known time periodwith a chemically reactive reagent during fluidic levitation of thesubstrate by controlling the composition of matter of a compositionallysegregated fluid flow during fluidic levitation of a substrate whereinthe fluid is either a gas or a liquid. It is an objective of theinvention to provide and an apparatus for dosing a surface of afluidically levitated substrate with a pre-determined quantity of areactive reagent to control the composition of matter of acompositionally segregated fluid flow during fluidic levitation of asubstrate wherein the fluid is either a gas or a liquid.

Another embodiment of the invention provides a method for producingcompositionally segregated fluid flows with at least one chemicallyreactive compositionally segregated region for the purpose of substrateprocessing of at least one surface of the levitated substrate duringfluidic levitation of a substrate wherein the fluid is either a gas or aliquid. An objective of the invention is to provide an apparatus forproducing compositionally segregated fluid flows with at least onechemically reactive compositionally segregated region for the purpose ofsubstrate processing of at least one surface of the levitated substrateduring fluidic levitation of a substrate.

One or more of the embodiments of the present invention for providingcompositionally segregated chemically reactive flows for the purposes offluidic levitation of a substrate with a levitation stabilizingstructure and substrate processing of at least one surface of thesubstrate during fluidic levitation is achieved using fluidic levitationof substrate with a levitation stabilizing structure using fluid flowscomprised of coaxial compound jets or collinear compound jets. Anadditional embodiment of the invention provides an apparatus for fluidiclevitation of substrates with levitation stabilizing structurescomprised of a stationary fluid emitting support provided with a meansto supply compositionally segregated fluid jets, said compositionallysegregated jets being either coaxial compound fluid jets or collinearcompound fluid jets. The embodiments providing coaxial compound jets orcollinear compound jets for the purpose of utilizing compositionallysegregated chemically reactive flows during fluidic levitation of asubstrate with a levitation stabilizing structure can be accomplishedusing an apparatus for fluidic levitation with coaxial compound jets oran apparatus for fluidic levitation with collinear compound jets.

The embodiments described above that provide positionally stablelevitation during fluid exposure that occurs during fluidic levitation,including fluid exposure to chemically reactive fluids, can be achievedby a method for fluidically levitating a substrate comprised of thesteps in order:

providing a substrate;

providing a levitation stabilizing structure on a surface of asubstrate, said levitation stabilizing structure overlaying andcontacting the substrate surface in a conformal-wise manner;

positioning the substrate proximate to a fluid emitting surface of astationary fluid emanating support in a conformal-wise manner with thelevitation stabilizing structure overlaying and contacting the surfaceof the substrate and facing the stationary fluid emanating surfacethrough which fluid will flow;

aligning the centroid of the interior confined area of the levitationstabilizing structure with at least one alignment feature on the surfaceof the stationary fluid emanating support;

initiating at least one collimated fluid flow from the stationary fluidemanating support surface to produce a collimated fluid jet such thatthe collimated fluid flow from the collimated fluid jet impinges on atleast one point of the opposing surface in an orthogonal manner wherethe point of fluid impingement is located within the interior confinedarea of the levitation stabilizing structure;

controlling the collimated fluid flow emanating from the stationaryfluid emanating support to fluidically levitate the substrate andlevitation stabilizing structure proximate to the surface of thestationary fluid emanating support; and

controlling the composition of the fluids employed during levitationusing an apparatus for production of compound fluid flows and jets thatproduces compositionally segregated reactive fluid flows.

The aforementioned fluid levitation method requires providing alevitation stabilizing structure on the surface of a substrate, saidlevitation stabilizing structure overlaying the substrate surface andcontacting the substrate surface and facing or opposing a stationaryfluid emitting surface through which fluid will flow in a conformal-wisemanner from whence at least one fluid jet emanates and impingesperpendicularly on the opposing moveable substrate surface to befluidically levitated. In the case of pneumatic levitation, at least onecollimated fluid gaseous jets impinging upon the movable substratesurface may impinge in an orthogonal manner; however, at least onecollimated fluid gaseous jets impinging in a non-orthogonal manner canbe additionally employed, depending on the desired levitationapplication. A collimated fluid gaseous jet impinging upon the movablesubstrate in an orthogonal or perpendicular-wise manner is employed whena minimum of substrate motion is desired during fluid levitation andprocessing. A collimated fluid gaseous jet impinging upon the movablesubstrate surface in a non-orthogonal or non-perpendicular manner can beemployed when initiation of substrate motion, for example, rotationalmotion, is desired during fluidic levitation and processing.

As will be described later, a method for controlling the composition ofthe fluids employed for levitation is provided using an apparatus forproduction of compound fluid flows and jets. The apparatus forproduction of compound fluid flows and jets also provides a way ofproducing a compositionally segregated reactive fluid flow for fluidiclevitation applications that is non-reactive with the fluid deliverysystem employed for the distribution of said reactive fluids.

The method of fluidic levitation described above can be made compatiblewith fabrication processes found, for example, in a fabrication facilityfor semiconductor circuits by the addition of the steps comprising inorder:

1. discontinuing the collimated fluid flow emanating from the stationaryfluid emanating support to discontinue the fluidic levitation of thesubstrate and levitation stabilizing structure proximate to the surfaceof the fluid emanating stationary support; and

2. removing the substrate and levitation stabilizing structure from thesurface of the stationary fluid emanating support.

Alternatively, this method of fluidic levitation can be made morecompatible with fabrication processes found, for example, in afabrication facility for semiconductor circuits by the addition of thesteps comprising in order:

1. removing the substrate and levitation stabilizing structure from thefluid flow emanating from the stationary fluid emanating support; and

2. discontinuing the collimated fluid flow emanating from the stationaryfluid emanating support through which fluid will flow to discontinue thefluid flow enabling the fluidic levitation of the substrate andlevitation stabilizing structure proximate to the surface of the fluidemanating stationary support.

This procedure allows for removal of the moveable substrate from thefluid flow emanating from the stationary fluid emanating support using,for example, a vacuum wand to minimize particle generation on thesurface of the moveable substrate during the removal of the moveablesubstrate from the stationary fluid emitting support.

The aforementioned procedures disclose a non-destructive method forstable fluid levitation of a substrate comprised of providing alevitation stabilizing structure attached to the surface of a substrate,said levitation stabilizing structure providing a means to achievestable fluidic levitation of a substrate for processing; fluidicallylevitating the substrate and levitation stabilizing structure byemploying a collimated fluid jet impinging in an orthogonal manner onthe substrate surface; controlling the composition of the impingingfluid jet during fluidic levitation using an apparatus for production ofcompound fluid flows and jets; discontinuing the fluidic levitation ofthe substrate and levitation stabilizing structure; and the removing thelevitation stabilizing structure after the levitation process. Theremoval of the levitation stabilizing structure from the substrate afterprocessing is highly desirable for process compatibility with the manyexisting workflows, such as those utilized for integrated circuitmanufacture. The removal of the levitation stabilizing structure fromthe surface of the substrate can be accomplished by many differentmethods including plasma etching, chemical dissolution, sand blasting,melting, scraping, or any other means known in the art for disassemblyand removal of surface layers and structures from substrates. Plasmaetching and chemical dissolution, including such methods as resist-liftoff, are contemplated and considered preferred methods for removal ofthe levitation stabilizing structure in order to minimize substratecontamination and damage during the levitation stabilizing structureremoval process.

The objective of providing a method for producing fluid flows containingchemically reactive substances for the purpose of fluidic levitation ofa substrate wherein the fluid is either a gas or a liquid and the fluidexhibits minimal chemical interaction with the fluid delivery systememployed in the fluidic levitation process can be achieved by employinga coaxial compound jet in the following method comprised of thefollowing steps:

1. providing a substrate with a levitation stabilizing structure;

2. providing a stationary fluid emitting support through which fluidwill flow with at least one fluid collimating conduit for producing anorthogonal jet, said fluid collimating conduit being in fluidcommunication with an apparatus for producing a coaxial compound laminarfluid flow from two or more fluid flows;

3. placing the substrate with the levitation stabilizing structure onthe stationary support through which fluid will flow with substratesurface containing the levitation stabilizing structure opposite andopposing the fluid collimating conduit of the stationary fluid emittingsupport and aligning the substrate to an alignment feature of thestationary fluid emitting support;

4. initiating fluid flow of at least two fluids, one of which ischemically inert and one of which is chemically reactive in theapparatus for producing a coaxial compound laminar fluid flow that is influid communication with the fluid collimating conduit of the stationaryfluid emitting support through which fluid will flow to producing acoaxial compound laminar fluid flow; said compound coaxial laminar fluidflow being comprised of an outermost region contacting the fluiddelivery system that is surrounding and overlaying at least onecontinuous interface of an inner region; said fluid flow in theoutermost region of the coaxial compound laminar fluid flow beingchemical non-reactive; said fluid flow in the interior region of thecompound coaxial flow containing chemically reactive substances, saidapparatus being in fluid communication with the fluid collimatingconduit of the fluid emitting stationary support through which fluidwill flow;

5. producing an orthogonal coaxial compound laminar fluid flow with saidapparatus by applying the compound coaxial laminar fluid flow to thefluid collimating conduit of the stationary fluid emitting supportthrough which fluid will flow under pressure to provide an orthogonalcoaxial compound jet that is orthogonal to the substrate surface withlevitation stabilizing structure; said compound fluid flow beingcomprised of an outermost region surrounding and overlaying at least onecontinuous interface of an inner region; said fluid flow in theoutermost region of the coaxial compound laminar fluid flow beingchemical non-reactive; said fluid flow in the interior region of thecompound coaxial flow containing chemically reactive substances, saidapparatus being in fluid communication with the fluid collimatingconduit of the fluid emitting stationary support; and

6. levitating the substrate with the levitation stabilizing structurewith fluid flow from said orthogonal coaxial compound jet.

The objective of providing a method for producing fluid flows containingchemically reactive substances for the purpose of fluidic levitation ofa substrate wherein the fluid is either a gas or a liquid and the fluidexhibits minimal chemical interaction with the fluid delivery systememployed in the fluidic levitation process can be achieved by employinga collinear compound jet in the following method comprised of thefollowing steps:

1. providing a substrate with a levitation stabilizing structure;

2. providing a stationary fluid emitting support through which fluidwill flow with at least one fluid collimating conduit for producing anorthogonal jet, said fluid collimating conduit being in fluidcommunication with an apparatus for producing a collinear compoundlaminar fluid flow from two or more fluid flows;

3. placing the substrate with the levitation stabilizing structure onthe stationary support through which fluid will flow with substratesurface containing the levitation stabilizing structure opposite andopposing the fluid collimating conduit of the stationary fluid emittingsupport and aligning the substrate to an alignment feature of thestationary fluid emitting support;

4. initiating fluid flow of at least two fluids, one of which ischemically inert and one of which is chemically reactive in theapparatus for producing a collinear compound laminar fluid flow that isin fluid communication with the fluid collimating conduit of thestationary fluid emitting support through which fluid will flow toproducing a collinear compound laminar fluid flow; said compoundcollinear laminar fluid flow being comprised of an outermost regioncontacting the fluid delivery system that is surrounding and overlayingat least one continuous interface of an inner region; said fluid flow inthe outermost region of the collinear compound laminar fluid flow beingchemical non-reactive; said fluid flow in the interior region of thecompound collinear flow containing chemically reactive substances, saidapparatus being in fluid communication with the fluid collimatingconduit of the fluid emitting stationary support through which fluidwill flow;

5. producing an orthogonal collinear compound laminar fluid flow withsaid apparatus by applying the compound collinear laminar fluid flow tothe fluid collimating conduit of the stationary fluid emitting supportunder pressure to provide an orthogonal collinear compound jet that isorthogonal to the substrate surface with levitation stabilizingstructure; said compound fluid flow being comprised of an outermostregion surrounding and overlaying at least one continuous interface ofan inner region; said fluid flow in the outermost region of thecollinear compound laminar fluid flow being chemical non-reactive; saidfluid flow in the interior region of the compound collinear flowcontaining chemically reactive substances, said apparatus being in fluidcommunication with the fluid collimating conduit of the fluid emittingstationary support through which fluid will flow; and

6. levitating the substrate with the levitation stabilizing structurewith the fluid flow from said orthogonal collinear compound jet.

Note that the method is distinguished from that of Hertz (U.S. Pat. No.4,196,437) because there is no stationary fluid involved in thisembodiment to form compound collinear jets. It is also distinguishedfrom both U.S. Pat. No. 3,368,760 and U.S. Pat. No. 3,416,730 throughthe use of collinear rather than coaxial jets.

The objective of providing a method for producing fluid flows containingchemically reactive substances for the purpose of fluidic levitation ofa substrate wherein the fluid is either a gas or a liquid and the fluidexhibits minimal chemical interaction with the fluid delivery systememployed in the fluidic levitation process can be further achieved byemploying a collinear or coaxial compound jet in the following methodcomprised of the following steps:

1. providing a substrate with a levitation stabilizing structure;

2. providing a stationary fluid emitting support through which fluidwill flow with at least one fluid collimating conduit for producing anorthogonal jet, said fluid collimating conduit being in fluidcommunication with an apparatus equipped with a means to control fluidcomposition for producing a coaxial or collinear compound laminar fluidflow from one or more fluid flows;

3. placing the substrate with the levitation stabilizing structure onthe stationary support with substrate surface containing the levitationstabilizing structure opposite and opposing the fluid collimatingconduit of the stationary fluid emitting support and aligning thesubstrate to an alignment feature of the stationary fluid emittingsupport through which fluid will flow;

4. initiating a fluid flow of a single, chemically inert fluid toproduce a laminar fluid flow that is in fluid communication with thefluid collimating conduit of the stationary fluid emitting supportthrough which fluid will flow producing a laminar fluid flow;

5. producing an orthogonal laminar fluid flow of chemically inert fluidwith said apparatus by applying the laminar fluid flow to the fluidcollimating conduit of the stationary fluid emitting support underpressure to provide an orthogonal jet that is orthogonal to thesubstrate surface with levitation stabilizing structure; said fluid flowbeing chemically non-reactive; said apparatus being in fluidcommunication with the fluid collimating conduit of the fluid emittingstationary support through which fluid will flow;

6. levitating the substrate with the levitation stabilizing structureusing the orthogonal jet of chemically non-reactive, chemically inertfluid;

7. initiating fluid flow of at least two distinct fluids in saidapparatus equipped with a means to control fluid composition forproducing a coaxial or collinear compound laminar fluid flow from one ormore fluid flows, wherein one of the fluids is chemically inert and asecond fluid is chemically reactive; wherein the apparatus for producinga coaxial or collinear compound laminar fluid flow from at least thefirst and second fluid is in fluid communication with the fluidcollimating conduit of the stationary fluid emitting support throughwhich fluid will flow to allow a coaxial or collinear compound laminarfluid flow through said fluid collimating conduit; said compound coaxialor collinear laminar fluid flow being comprised of an outermost regioncontacting the fluid delivery system that is surrounding, in contact,and overlaying at least one continuous interface of an inner region;said fluid flow in the outermost region of the coaxial or collinearcompound laminar fluid flow being comprised essentially of the firstchemical non-reactive fluid; said fluid flow in the interior region ofthe compound coaxial or collinear flow being comprised essentially ofthe second chemically reactive fluid containing chemically reactivesubstances or materials, said apparatus being in fluid communicationwith the fluid collimating conduit of the fluid emitting stationarysupport through which fluid will flow;

8. producing an orthogonal coaxial or collinear compound laminar fluidflow with said apparatus by applying the compound coaxial or collinearlaminar fluid flow to the fluid collimating conduit of the stationaryfluid emitting support under pressure to provide an orthogonal coaxialor collinear compound jet that is orthogonal to the substrate surfacewith levitation stabilizing structure; said compound fluid flow beingcomprised of an outermost region contacting, surrounding, and overlayingat least one continuous interface of an inner region; said fluid flow inthe outermost region of the coaxial or collinear compound laminar fluidflow being chemical non-reactive; said fluid flow in the interior regionof the compound coaxial or collinear flow containing chemically reactivesubstances, said apparatus being in fluid communication with the fluidcollimating conduit of the fluid emitting stationary support throughwhich fluid will flow; and

9. levitating the substrate with the levitation stabilizing structureusing the orthogonal coaxial or collinear compound jet comprised of atleast one chemically reactive fluid emanating from the stationary fluidemitting support.

The repetition of the last six steps will allow exposure of thesubstrate surface with levitation stabilizing structure to differentchemically reactive fluids whilst controlling the contact of thechemically reactive fluids with critical components of the fluiddelivery system. The process above can be further modified after thelast step by the following steps:

1. initiating a fluid flow of a single, chemically inert fluid toproduce a laminar fluid flow that is in fluid communication with thefluid collimating conduit of the stationary fluid emitting supportthrough which fluid will flow producing a laminar fluid flow;

2. producing an orthogonal laminar fluid flow of chemically inert fluidwith said apparatus by applying the laminar fluid flow to the fluidcollimating conduit of the stationary fluid emitting support throughwhich fluid will flow under pressure to provide an orthogonal jet thatis orthogonal to the substrate surface with levitation stabilizingstructure; said fluid flow being chemically non-reactive; said apparatusbeing in fluid communication with the fluid collimating conduit of thefluid emitting stationary support;

3. levitating the substrate with the levitation stabilizing structureusing the orthogonal jet of chemically non-reactive, chemically inertfluid;

4. discontinuing the collimated fluid flow of the chemicallynon-reactive, chemically inert fluid emanating from the stationary fluidemanating support to discontinue the fluidic levitation of the substrateand levitation stabilizing structure proximate to the surface of thefluid emanating stationary support through which fluid will flow; and

5. removing the substrate and levitation stabilizing structure from thesurface of the stationary fluid emanating support through which fluidwill flow.

In an alternative embodiment steps 13 and 14 can be reversed to minimizeparticle generation while removing the sample.

In one alternative embodiment of the above procedure, step 3 isperformed after step 4 and step 5 have been executed so that thecollimated fluid jet of chemically non-reactive fluid from thestationary fluid emitting support can be established before the moveablesupport is aligned to the stationary support. When step 3 is performedafter the collimated fluid jet is established in step 5, the moveablesupport is aligned with the stationary support and released from aholder while the collimated fluid jet is flowing resulting in samplelevitation when the moveable support is placed over the stationary fluidemanating support

Steps 1-14 provide a method for processing a substrate with a levitationstabilizing structure in contact with and overlaying the substratesurface to be processed using fluidic levitation with coaxial orcollinear compound jets containing chemically reactive species. Thechemically reactive species in the coaxial or collinear compound jet mayhave reactivity that is additionally accelerated by other processingfactors such as heat, pressure, ionizing radiation, or chemical reactionwith one or more additional chemically reactive species in the compoundcollinear or coaxial jet. For example, temperature is an effective wayof accelerating the chemical kinetics of surface processes. Thus, theinteraction between chemically reactive species in the fluid and thesubstrate surface can be influenced by controlling the temperature ofthe levitating fluid containing the chemically reactive species, thetemperature of the levitating substrate, or both the levitating fluidand the levitating substrate. In another embodiment, the interactionbetween chemically reactive species in the fluid employed for fluidiclevitation and the substrate surface can be influenced by ionizingradiation. For example, said ionizing radiation can be ultravioletradiation that is employed to induce photochemical reactions between thechemically reactive species in the fluid flow employed for substratelevitation and the substrate surface. Further, if two or more reactivespecies are present in an orthogonal jet employed for fluidic levitationof a substrate, then the two reactive species can be chosen to reactwith each other during the fluidic levitation process thereby producinga third reactive species that selectively interacts with the surface ofthe substrate during fluidic levitation of said substrate with acompound fluid flow. It is contemplated, for example, that heat,radiation, or pressure may activate one or more reactive species in acompound fluid flow to promote the formation of new reactive species inthe compound fluid flow employed for fluidic levitation, said newreactive species interacting with the surface of the fluidicallylevitating substrate.

FIG. 11 shows a cross-sectional view illustrating one embodiment of theprior art disclosed in U.S. Pat. No. 5,370,709. U.S. Pat. No. 5,370,709discloses a stationary support through which fluid will flow 12 containsa single fluid collimating conduit 14 that is in fluid communicationwith a pressurized manifold (not shown). The single fluid collimatingconduit 14, also called an orifice, nozzle, or bore produces a singleorthogonal jet whose velocity vector indicated by the arrows in FIG. 11is normal to a surface of moveable substrate 10 at the impingementlocation of the jet onto the moveable substrate surface and to thesurface of stationary support through which fluid will flow 12. Theorthogonal jet thus impinges in an orthogonal fashion on the opposingsurface of moveable substrate 10. Stationary support 12 also contains atleast one protruding feature 26 extending above the surface of support12 in the direction of moveable substrate 10 and is located on thesurface of stationary support 12 so as to impede horizontal lateralmotion of moveable substrate 10 in the direction parallel to surface 24of stationary support 12. FIG. 11 illustrates the use of physical stops,exemplified by protruding feature 26, that is commonly employed for thepurposes of stabilizing the position of the moveable substrate duringfluidic levitation so that the moveable substrate 10 remains essentiallycentered over the single fluid collimating conduit 14 that supplies anorthogonal jet whose velocity vector is normal to the stationary supportsurface 24. The location of the fluid collimating conduit, nozzle, bore,or orifice in the gas emanating surface is taken as an alignment featureand the substrate is positioned at a desired location relative to thealignment feature. The locations of the protruding features 26 can alsobe taken as alignment features for positioning of the substrate at adesired location before initiating the fluid flow required for pneumaticlevitation. A fluid inlet 58 is provided to allow fluid communicationbetween fluid collimating conduit 14 and a pressurized reservoir ofchemically inert fluid. A second fluid inlet 56 is provided proximate tofluid collimating conduit 14 to allow fluid communication between fluidcollimating conduit 14 and a pressurized reservoir of chemicallyreactive fluid. At the fluid inlet intersection region 57 indicated inthe FIG. 11, the fluid from inlet 58 and inlet 56 mix to form ahomogeneous fluid of uniform composition of matter. The fluid mixtureflows through fluid collimating conduit 14 from whence a chemicallyreactive fluid jet is delivered into the volume region between themoveable substrate 10 and the stationary fluid emitting support 12. Thechemically reactive fluid is always in contact with the fluid deliverysystem and U.S. Pat. No. 5,370,709 specifically teaches that the fluidinlet intersection region 57 must be close to fluid collimating conduit14 in order to minimize deposition of undesirable material in fluidcollimating conduit 14 as a result of contact of chemically reactivefluid from fluid inlet 56 with the fluid collimating conduit region 14of the fluid delivery system. U.S. Pat. No. 5,370,709 employs achemically reactive material that undergoes thermal decomposition toform a coating on substrate 10. U.S. Pat. No. 5,370,709 teaches thatcontrol of fluid and apparatus temperatures can be used to mitigate theundesirable thermal decomposition of the chemically reactive fluid inthe fluid delivery system. U.S. Pat. No. 5,370,709 does not teach anymethod to manage the contact between the chemically reactive fluid andthe fluid delivery system elements like fluid collimating conduit 14other than to minimize the residence time of the chemically reactivefluid in the fluid delivery system by minimizing the length of tubingthat the chemically reactive fluid must traverse in the fluid deliverysystem.

FIG. 12 is a cross-sectional view illustrating one embodiment of thepresent inventive method for practicing pneumatic levitation. FIG. 12shows a moveable substrate 10 with a levitation stabilizing structure 30fabricated thereupon where the surface of moveable substrate 10 with thelevitation stabilizing structure 30 opposes the gas emanating surface ofstationary support through which gaseous fluid will flow 12 with fluidcollimating conduit 14. Fluid collimating conduit 14 is in fluidiccommunication through fluid outlet 19 with a pressurized fluidic flowemanating from an apparatus for production of compound fluid flows andjets 20 which is, in turn, in fluidic communication with fluid inlet 58and fluid inlet 56.

FIG. 12 illustrates the appropriate relative positions of the elementsmoveable substrate 10 with levitation stabilizing structure 30 relativeto the stationary support 12 and fluid collimating conduit 14 for theuse of levitation stabilizing structure 30 to be effective as a methodof positional stabilization during fluidic levitation with an orthogonaljet emanating from fluid collimating conduit 14. It has been found thatthe use of the levitation stabilizing structure as a method forimproving the lateral stability of a moveable substrate during pneumaticlevitation only requires that the fluid jet from jet forming fluidcollimating conduit 14 of stationary support 12 impinge on the surfaceof moveable substrate 10 within the interior impingement area defined bythe surface bounded and enclosed by the walls of the levitationstabilizing structure 30 fabricated on the surface of moveable substrate10. It is preferred that the fluid jet from jet forming fluidcollimating conduit 14 of stationary fluid emitting support 12 impingeon the surface of moveable substrate 10 near the centroid of interiorimpingement area defined by the area enclosed by the interior walls ofthe levitation stabilizing structure 30 fabricated on the surface ofmoveable substrate 10. It is preferable that the centroid of theinterior impingement area enclosed by the interior walls of thelevitation stabilizing structure 30 fabricated on the surface ofmoveable substrate 10 be located within the impingement area enclosed bythe interior walls of the levitation stabilizing structure 30. The fluidcollimating conduit on the stationary fluid emitting support is analignment feature on the surface of the stationary fluid emanatingsupport and the centroid of the interior impingement area of thelevitation stabilizing structure is aligned with the alignment featurewherein the alignment feature is a fluid collimating conduit on thesurface of the stationary fluid emanating support. Thus, one embodimentof a method for fluidic levitation comprises the steps of:

1. providing a substrate;

2. fabricating a levitation stabilizing structure on a surface of asubstrate;

3. positioning the substrate proximate to a fluid emitting surface of astationary fluid emanating support in a conformal-wise manner with thelevitation stabilizing structure overlaying the surface of the substrateand facing the stationary fluid emanating surface;

4. aligning the centroid of the interior impingement area of thelevitation stabilizing structure with at least one alignment feature onthe surface of the stationary fluid emanating support;

5. initiating at least one collimated fluid flow from the stationaryfluid emanating support surface to produce a collimated fluid jet, and;

6. controlling the collimated fluid flow emanating from the stationaryfluid emanating support to fluidically levitate the substrate andlevitation stabilizing structure proximate to the surface of thestationary fluid emanating support.

It has been observed experimentally that the alignment of the centroidof the interior impingement area of the levitation stabilizing structurewith at least one alignment feature on the surface of the stationaryfluid emanating support is not highly critical as the levitationstabilizing structure exhibits self-alignment during the levitationprocess. The reasons for self-aligning behavior during pneumaticlevitation are described in more detail below. This is a distinctadvantage of using a levitation stabilizing structure during pneumaticlevitation.

FIG. 12 also shows an apparatus for production of compound fluid flowsand jets 20. The compound jet forming apparatus 20 will be described inmore detail later and is comprised of multiple elements includingmechanisms for providing a means for controlling the temperature,pressure, and flow of at least one fluid. Apparatus 20 in FIG. 12 alsoprovides and includes a means for controlling the composition of thecompound fluid flow. The compound fluid flow forming apparatus 20 shownin FIG. 12 has two inlets. Fluid inlet 56 allows a first fluid to flowinto apparatus 20 and fluid inlet 58 allows a second fluid to flow intoapparatus 20. Apparatus 20 has a fluid outlet 19 in fluid communicationwith fluid collimating conduit 14. In one embodiment, apparatus 20 is influid communication with at least one pressurized-gas sources providinga gas flow through the fluid collimating conduit 14 and impinging on themoveable substrate surface within the enclosed interior impingement areaof the moveable substrate sufficient to levitate the moveable substrateand expose the moveable substrate to the gas while restricting thelateral motion of the moveable substrate with the levitation stabilizingstructure.

The function of apparatus 20 is to combine at least 2 fluid flows, afirst fluid flow and a second fluid flow, to form a compositionallysegregated compound fluid flow exiting apparatus 20 through outlet 19and flowing though fluid collimating conduit 14 of the stationary fluidemitting support through which fluid will flow. Apparatus 20 is in fluidcommunication with a pressurized fluid source. In one embodiment,apparatus 20 is in fluid communication with a pressurized-gas source. Inanother embodiment, apparatus 20 is in fluid communication with apressurized-liquid source.

In one embodiment the first fluid flow can be a reactive fluid and thesecond fluid flow can be a non-reactive fluid. Unlike any of the priorart utilizing fluid flows for fluidic levitation, the compound fluidflow exiting apparatus 20 at fluid outlet 19 is a spatially non-uniformcomposition of matter comprised of a chemically reactive fluid flowencased and surrounded by a chemically non-reactive fluid flow. Aspatially non-uniform composition of matter is a composition of matterwhose chemical composition changes depending on the sampling locationwith the composition of matter volume. This compound fluid flowemanating from outlet 19 of apparatus 20 is injected through fluidcollimating conduit 14 to form a spatially non-uniform compound jetwhose fluidic components are distributed so that the compound jet isnon-reactive with the critical fluid contact regions of the fluiddelivery system employed for fluidic levitation. An additional functionof outlet 19 is to provide optional hydrodynamic focusing of the fluidflow. Hydrodynamic focusing or gas dynamic occurs when fluid flows ofdifferent velocity come into contact. It is preferred that the flowvelocity of all flows in apparatus 20 be limited so that the flowexhibits lamellar behavior. For example, a flow of primary fluid can besqueezed or expanded by the surrounding secondary fluid sheath to occupya smaller or larger cross-section by employing a suitable choice ofprimary and secondary fluid velocities. When the velocity of thesecondary fluid is larger than that of the primary fluid in a collinearcompound flow the primary fluid is “squeezed” to occupy a smallerpercentage of cross-sectional area of the compound flow. When thevelocity of the secondary fluid is less than that of the primary fluidin a collinear compound flow then the primary fluid expands to occupy alarger percentage of cross-sectional area of the compound flow.Hydrodynamic focusing provides an additional method for managingchemically reactive fluid flows. Contrary to the present invention, theuse of hydrodynamic or gas dynamic focusing as a result of velocitydifferences between the primary and secondary jet is taught as beingundesirable during compound jet formation and is not disclosed in eitherU.S. Pat. No. 3,368,760 or U.S. Pat. No. 3,416,730. There is no mentionor anticipation of the use of compound jets for fluidic levitationprocesses in either U.S. Pat. No. 3,368,760 or U.S. Pat. No. 3,416,730.

In the present inventions compound fluid flows are produced by apparatus20 by combining at least two fluid flows and minimizing the mixingbetween the two fluid flows. When only two fluid flows are present inapparatus 20, a first fluid flow and a second fluid flow, the secondfluid flow being an outer sheath fluid flow that is in contact with andsurrounds the first fluid flow for formation of a compound fluid flow,then the position of the first fluid flow within the outer sheath fluidflow distinguishes whether the compound fluid flow is coaxial jet orcollinear. The distinguishing feature of a coaxial compound fluid flowis that the centroids of the polygons defining the shape of thecross-sectional area of the fluid delivery tubes are all coincident asshown in FIGS. 15c and 15d . The distinguishing feature of a collinearcompound jet is that the centroids of the polygons defining the shape ofthe cross-sectional area of the fluid delivery tubes are not coincidentas shown in FIGS. 18c and 18d . A common feature of both coaxial andcollinear compound fluid flows is the presence of an outer sheath offluid surrounding, contacting, and encapsulating the first fluid flow.

Apparatus 20 optionally includes a mechanism providing a means foraccurately controlling the temperature, pressure, and flow of the fluidsthat are employed for the purpose of producing a collimated compoundfluid jet. Typical means for controlling pressure of gaseous fluidsinclude both passively and actively controlled pressure regulatorsincluding electronically controlled pressure regulators and other typesof pressure regulator methods known in the art. Typical temperaturecontrol mechanisms for a fluid include passive and actively controlledheating and cooling units including heat exchangers, heating tapes andcoils as well as cooling coils through which the fluid passes,temperature controlled reservoirs, and other mechanisms and devicesknown to those skilled in the art of temperature control of fluids.Temperature and pressure control loops employed to achieve stable fluidtemperatures and fluid pressures may incorporate the use automatedtemperature and pressure control units. Typical means for controllingthe flow of one or more gaseous fluids include the use of orifices ofknown diameter with known pressure-flow relationships, gas flow meters,flow controllers, control valves, and variable control valves of alltypes including mass flow meters and mass flow controllers, rotameters,Coriolis flow meters coupled with flow controllers, turbine flow meters,pitot based flow meters and other types of fluid flow meters familiar tothose skilled in the art of process control of flowing fluid media wherethe fluid is a liquid or a gas.

Controlling the fluid composition is an important feature of theapparatus, as taught by U.S. Pat. Nos. 3,368,760 and 3,416,730. Forexample, specific valve configurations can be employed in apparatus 20to allow the apparatus 20 to produce compound jets whose spatiallynon-uniform composition can be varied as a function of time as thecompound fluid flows through fluid collimating conduit 14. This is adistinct advantage because it allows the surface of moveable substrate10 that opposes the fluid emitting support to be exposed to aconcentration of a reactive fluid for a known amount of time. Exposureof a surface to a chemical species for a known amount of time is alsoknown as surface exposure or surface dosing and an apparatus thatprovides a means to dose a surface with a specific reactive fluid flowis extremely useful for fluidic levitation applications.

It is further recognized that the entire assembly represented by thecross-sectional view of FIG. 12 could be rotated by 180 around an axisnormal to the plane of FIG. 12 and the positional configuration willstill be functional. The use of a levitation stabilizing structure 30during fluidic levitation does not alter the function of a fluidiclevitation apparatus employing Bernoulli airflow with respect tophysical orientation of the apparatus, and in fact improves therobustness of fluidic levitation with respect to tilting of thegas-emanating stationary support through which fluid will flowregardless of the apparatus attitude and orientation. Fluidic levitationcan take place when the velocity vector of the orthogonal fluid jet isessentially parallel to the gravitational force vector or when thevelocity vector of the orthogonal fluid jet is essentially anti-parallelto the gravitational force vector. The presence of a levitationstabilizing structure 30 on the moveable substrate surface does notalter the relationships between the pneumatic forces that are generatedby the fluid flow from the orthogonal jet that flows between thesubstrate surface and the fluid emitting support surface and thegravitational force vector that are inherently present in fluidiclevitation processes employing Bernoulli airflow. This is a distinctadvantage of the invention.

It is recognized that the stationary support through which fluid willflow is not restricted to a planar configuration as illustrated in FIG.12. The features of the stationary support through which fluid will flowcomprise the following: the stationary fluid emitting support containsat least one fluid collimating conduit in fluid communication with amanifold and a pressurized fluid source, said fluid collimating conduithaving a cross-sectional area less than or equal to ¼ of the surfacearea of the interior impingement area of the levitation stabilizingstructure; the surface area of the stationary fluid emitting support isat least equal to the surface area of the interior impingement area onthe moveable substrate; and the fluid flow between the stationarysupport and the moveable substrate is characterized by radial flowpatterns that are essentially symmetric with respect to the centroid ofthe interior impingement area. It is preferred that said fluidcollimating conduit have a cross-sectional area less than or equal to ¼of the impingement area enclosed by the walls of the levitationstabilizing structure.

Thus, in one embodiment, if the moveable substrate surface follows theshape of an arc, as is found, for example, on the surface of an opticallens, then a stationary support surface can be fabricated that followsthe surface features of the moveable substrate surface and is conformalto the surface features of the moveable substrate surface and produces aradial flow pattern when an orthogonal jet impinges on the moveablesubstrate surface. Thus, the stationary support is fabricated to followthe surface features of the moveable substrate surface in aconformal-wise manner. In another embodiment, the stationary supporttopography resembles a mold of the surface of the moveable substrate. Inanother embodiment, the stationary support topography follows thenegative three dimensional image of the surface of the moveablesubstrate. It is preferred that the surface topography of moveablesubstrate 30 be continuous and smooth, monotonically varying without asignificant number of topographical disparities; however, practicalexperience has shown that topographical disparities are well toleratedby fluidic levitation processes. In particular, topographicaldisparities are well tolerated by fluidic levitation processes when thetopographical disparity protrusion distance as measured normal to thesubstrate surface is smaller than the average thickness of the fluidlayer formed between the substrate and the stationary fluid emittingsupport through which fluid will flow during fluidic levitation.

The function of the levitation stabilizing structure (LSS), fabricatedon the moveable substrate surface is to harness the inherent kineticenergy of the gaseous flow of the fluidic layer employed in fluidiclevitation so as to convert said kinetic energy into directional forcesfor the purpose of introducing positionally restorative forces that actin a restorative manner to control and minimize undesirable lateralmovement of the moveable substrate during fluidic levitation. The LSS isuseful when the fluid used for fluidic levitation is a gas or a liquid.Fluidic levitation employing a gaseous fluid is called pneumaticlevitation. Fluidic levitation employing a condensed phase liquid fluidis called hydraulic levitation.

The symmetric radially outward flow which occurs during pneumaticlevitation processes employing one or more orthogonal jets can thus beharnessed to achieve positional stability of a pneumatically levitatedmoveable substrate using a levitation stabilizing structure fabricatedon the opposing surface of the moveable substrate. Furthermore, thefluid flow from one or a plurality of orthogonal or tilted compound jetscontains substantial pneumatic energy in the form of both kinetic andpotential energy and this unharnessed pneumatic energy can be used toachieve positional stability of a pneumatically levitated moveablesubstrate.

Positional stability of the moveable substrate during pneumaticlevitation is achieved readily when the stationary gas emitting supportthrough which gaseous fluid will flow contains fluid collimatingconduits, nozzles, bores, and orifices used for the generation ofgaseous jets—tilted or orthogonal—that impinge within the interiorimpingement area on the surface of the opposing moveable substrate thatis within the confines of the area enclosed by the walls of thelevitation stabilizing structure that is located on and in contact withthe moveable substrate surface that opposes and faces the stationary gasemitting support surface, as shown in FIG. 12. The location of thelevitation stabilizing structure on the moveable substrate is a featurethat distinguishes the inventive method from all other previous attemptsto address positional stability during pneumatic levitation.Furthermore, the inventive method is not restricted to planar plate-likesubstrates although planar substrates are preferred. Additionally, asshown in FIG. 12, the use of compound jets during fluidic levitation isa distinguishing feature of the inventive method from all other previousattempts to address delivery of chemically reactive fluids duringfluidic levitation.

FIGS. 13a through 13c illustrate the application of a levitationstabilizing structure to a moveable substrate having a three-dimensionalspherical surface topography. FIG. 13a is a cross-sectional view of anon-planar moveable substrate 10 with levitation stabilizing structure30 overlaying and in contact with one surface of non-planar moveablesubstrate 10 wherein non-planar moveable substrate 10 is positioned overa gas-emanating stationary support 12 containing a fluid collimatingconduit 14 in fluid communication with a source of at least one fluidwhose pressure, temperature, and flow can be controlled by, for example,the previously disclosed apparatus 20. In one embodiment, the non-planarmoveable substrate 10 is a circular convex lens. The gas-emanatingstationary support 12 has surface topography that is conformal to thesurface topography of non-planar moveable substrate 10. In other words,the general contours of the surface of the stationary gas emittingsupport 12 follow the contours of the surface of moveable substrate 10in a conformal-wise manner as if the surface of moveable substrate 10without the levitation stabilizing structure had been imprinted bypressure on the surface of the stationary gas emitting support 12 andsaid surface of gas emitting support deformed to replicate the negativetopography of the non-planar moveable substrate surface. FIGS. 13b and13c shows two plan views of two embodiments of a levitation stabilizingstructure on the non-planar moveable substrate 10 of FIG. 13a that arecompatible with the stationary fluid emitting support configurationshown in FIG. 13a . The plan view is directly down the proper rotationaxis of symmetry of the levitation stabilizing structure so that therotational symmetry of the levitation stabilizing structure 30 can beseen. FIG. 13b shows a circular levitation stabilizing structure 30 witha proper rotational axis of symmetry 40 that is a C_(∞) axis that hasbeen fabricated on the non-planar moveable substrate 10. FIG. 13c showsa pentagonal levitation stabilizing structure 30 with a properrotational axis of symmetry 40 that is a C₅ axis that has beenfabricated on the non-planar moveable substrate 10.

Thus, a further advantage of the method of fluidic levitation employinga levitation stabilizing structure is the fluidic levitation ofarbitrarily shaped substrates and the processing of selective portionsof the surface area of said arbitrarily shaped substrates. In theembodiments shown above in 5 a through 5 c, the levitation stabilizingstructure can be formed on arbitrarily shaped substrate thereby enablingpneumatic levitation of the arbitrarily shaped substrate when the planeof the levitation stabilizing structure is positioned normal to andfacing an orthogonal jet emanating from a stationary support. Asmentioned previously, the levitation stabilizing structure additionallyenables the use of pneumatic levitation with, for example, planarsubstrates that are shaped like circles, triangles, squares, and otherpolygonal shapes. The levitation stabilizing structure is particularlyuseful for pneumatic levitation of silicon wafers that are essentiallycircular shaped and are additionally marked with a flat or notch so thatthe wafer is not perfectly symmetric. Wafers marked with a flat can beconsidered to be arbitrarily shaped substrates and the levitationstabilizing structure is particularly useful for pneumatic levitation ofsamples of this type. Additionally, the levitation stabilizing structurecan be employed with three dimensional moveable substrates, saidsubstrates being planar or non-planar, to enable processing of selectedregions on the substrate surface.

In a general embodiment, the moveable substrate is not necessarilyplanar and can be topographically complex as in the case of, forexample, a spherical shaped substrate. In another embodiment, themoveable substrate can be mostly planar but additionally possessingthickness variations such as decorative or functional patternsfabricated upon the surface. The moveable substrate may possessthickness variations characteristic of three dimensional objects givingrise to surface topographies that are either monotonically concave ormonotonically convex. In another embodiment of the use of the levitationstabilizing structure, a regular symmetrically shaped polygonallevitation stabilizing structure, such as a circular, pentagonal, orhexagonal levitation stabilizing structure, is fabricated upon thesurface of a sphere using, for example, patterning of a material layercomprised of a patternable material such as photoresist and a non-planargas-emanating stationary support is used for pneumatic levitation, thenon-planar gas-emanating stationary support comprising a concave surfacehaving an interior radius larger than or equal to the internal radius ofthe spherical object to be levitated and a single fluid collimatingconduit normal to the concave interior surface of the gas-emanatingstationary support: the surface of the gas-emanating stationary supportbeing an approximate 3 dimensional negative duplication of the threedimensional topography of the moveable substrate. The spherical moveablesubstrate, when placed inside the concave surface of the gas-emanatingstationary support and in contact with an orthogonal jet emanating fromthe concave surface of the gas-emanating stationary support structurewill pneumatically levitate and exhibit restricted motion preventing thespherical moveable substrate from tipping and the forces that producethe restricted motion are the result of balanced pneumatic forces whoseorigin lies in the interaction between the radial gas flow from theorthogonal jet and the levitation stabilizing structure. In general, thethree dimensional negative contours of the gas-emanating stationarysupport should approximately follow the three dimensional positivecontours of the moveable substrate to be pneumatically levitated. Whenthe three dimensional contours of the positive image topography of themoveable substrate become sufficiently small and the moveable substrateapproaches planarity there is less need for exact three dimensionalnegative duplication of the moveable substrate surface topography in thegas-emanating stationary support surface.

Thus, the use of the levitation stabilizing structure with a moveablesubstrate of arbitrary shape has wide applicability both to planar andthree dimensional moveable substrates. The levitation stabilizingstructure may follow a scaled projection outline of the perimeter of theplanar movable substrate upon which it is fabricated but, in otherembodiments, it can be suitable for the levitation stabilizing structureto be a polygonal shape that is different from circumferential polygonalshape of the moveable substrate upon which it is fabricated in order toobtain improved pneumatic levitation stability by optimizing the shape,area, and size of the levitation stabilizing structure with respect tothe shape, size, area, and mass of the moveable substrate upon which thelevitation stabilizing structure is fabricated.

FIG. 14 shows a process step diagram for the inventive Process 70 offluidically levitating a substrate with a levitation stabilizingstructure for the purpose of exposing the surface of a moveablesubstrate to a series of fluid flows where at least one fluid flow is achemically reactive fluid flow. Process 70 is comprised of 9 stepsdesignated steps 71 through 79. The process steps of process 70 aresequentially applied Steps 74 through 77 of Process 70 are sequentialsteps that can be repeated in a loop-wise manner for the purpose ofexposing the surface of the fluidically levitated moveable substrate tomore than one chemically reactive fluid flow and in one embodiment ofProcess 70 the moveable substrate with levitation stabilizing structureis fluidically levitated and exposed to a series of different fluidflows by repetition of steps 74 through 77 of Process 70. As shown instep 71, a moveable substrate with a levitation stabilizing structure onone surface is provided and the moveable substrate with levitationstabilizing structure is positioned proximate to the surface of thefluid emitting stationary support with the levitation stabilizingstructure opposed and facing the fluid emitting surface of thestationary support through which fluid will flow. The positioning stepalso comprises aligning the moveable substrate with alignment markingson the fluid emitting stationary support so that the fluid emitting fromthe stationary fluid emitting support will impinge proximate to thecentroid of the levitation stabilizing structure impingement area. It isnot necessary that the moveable substrate with levitation stabilizingstructure contact the stationary support during step 71. In anembodiment of process 70, the moveable substrate can be positioned usinga substrate holder such as a Bernoulli wand or a vacuum wand during step71. In step 72 a fluid flow of at least one chemically non-reactivefluid is initiated in the fluidic levitation apparatus to fluidicallylevitation the moveable substrate with levitation stabilizing structureusing an orthogonal fluid jet flowing from the surface of the stationaryfluid emanating support. In one embodiment the moveable substrate thatis positioned proximate to the stationary support in step 71 using asubstrate holder is released from the substrate holder after thenon-reactive fluid flow and fluidic levitation is initiated in step 72thereby allowing unimpeded levitation of the moveable substrate by thenon-reactive orthogonal fluid jet after which the substrate holder istemporarily removed so as to not interfere with fluidic levitation ofthe moveable substrate. In step 73 the moveable substrate is fluidicallylevitated with a chemically non-reactive fluid for a period of timeduring which various additional process related variables can beadjusted and stabilized. For example, during step 73 the fluid flowduring fluidic levitation can be employed as a means to ensure thatparticle contamination is minimized at the levitated moveable substratesurface by allowing the high velocity fluid flow in the volume regionbetween the stationary fluid emitting support and the moveable substrateto sweep particles off the surface of the substrate. In another processembodiment, the period of time elapsing during step 73 can be used toheat the levitating substrate to the desired temperature duringlevitation before exposure of the moveable substrate surface to achemically reactive fluid flow. Alternately, the timed period of fluidiclevitation in step 73 can be used to allow the substrate to come to anequilibrium position during fluidic levitation if the sample was notinitially positioned properly. Thus, step 73 is essentially a timedperiod wherein the apparatus with fluidically levitated moveablesubstrate is brought to the desired state of operation after initiatingthe fluidic levitation of the moveable substrate. Sequential step 74initiates chemically reactive fluid flow during the fluidic levitationprocess and provides a way exposing the surface of the moveablesubstrate with levitation stabilizing structure to the chemicallyreactive fluid flow. Apparatus 20 is employed as an apparatus providinga means to add chemically reactive species to the fluid flow through theproduction of compound fluid flows that are spatially non-uniform inchemical composition and are comprised of a primary chemically reactivefluid that is surrounded by and in contact with a sheath of a secondaryfluid that is chemically non-reactive. Exposure of the levitatingsubstrate surface to a chemically reactive compound fluid flow beginswhen apparatus 20 is employed to add the chemically reactive compound tothe fluid flow employed for substrate levitation during the fluidiclevitation of the substrate. In step 75 a period of time is allowed toelapse whilst the surface of the moveable substrate with levitationstabilizing structure is exposed to chemically reactive species in thefluid flow during fluidic levitation. Step 76 is sequentially carriedout at the end of the elapsed time period of step 75 and apparatus 20 isemployed as a means to change the fluid composition of the compound jetemployed during fluidic levitation and remove chemically reactive fluidsfrom the fluid flow employed for fluidic levitation of the substrate. Instep 77 a period of time is allowed to elapse to ensure that chemicallyreactive species have been swept out of the fluid flow employed forfluidic levitation and additionally ensure that the chemically reactivespecies have been swept out of the fluid volume employed as a fluidlayer between the moveable substrate and the stationary support duringfluidic levitation.

Process step diagram 70 shows that steps 74 through 77 can be repeatedas many times as necessary to expose the surface of the fluidicallylevitated moveable substrate to a series of fluid flows wherein at leastone fluid flow is a chemically reactive fluid flow. In one embodiment ofprocess step diagram 70, steps 74 through 77 can be repeated as manytimes as necessary to expose the surface of the pneumatically levitatedmoveable substrate to a series of gas flows wherein at least one gasflow is a chemically reactive gas flow. In one embodiment of the repeatsequence, each repeat of sequential step 74 through 77 may employchemically reactive flows with the same chemical compositions in thechemically reactive flows. In another embodiment of the repeat sequence,each time steps 74 through 77 are repeated a different chemicallyreactive flow from the previous repeat sequence of steps 74 through 77can be employed during the fluidic levitation process. After therequired number of repeats of steps 74 through 77 have been executed thenext sequential step in process 70 is step 78. In step 78 the chemicallynon-reactive fluid flow employed for fluidic levitation in step 77 isdiscontinued in order to terminate the fluidic levitation of thesubstrate. Step 78 may optionally be a timed step where the flow ofchemically non-reactive fluid is allowed to remain for a specific amountof time before being discontinued. In the last process step of process70 the moveable substrate is removed from the surface of the stationaryfluid emitting support in step 79. In an alternate embodiment of process70, step 78 is a timed step where the moveable substrate is fluidicallylevitated using a flow of chemically non-reactive fluid for a specificamount of time and in step 79 the moveable substrate is removed from thechemically non-reactive fluid flow using a substrate holder like avacuum wand or a Bernoulli wand and the chemically non-reactive fluidflow is discontinued. The alternate embodiments disclosed for process 70provide a way of further reducing particle contamination of the moveablesubstrate surface. Thus, process 70 discloses a sequence of steps thatprovide a process for fluidically levitating a substrate with alevitation stabilizing structure in a fluidic levitation apparatuscomprised of a stationary fluid emitting support with a fluidcollimating conduit providing a means to produce orthogonal jets from afluid flow and an apparatus in fluid communication with the stationaryfluid emitting support providing a means for controlling the compositionof the fluid flow of the orthogonal jet through the formation ofcompound fluid flows comprised of fluid flows with spatially non-uniformcompositions. In one embodiment, the process steps of process 70 providea method of pneumatically levitating a moveable substrate with a seriesof sequential gas flows wherein at least one of the sequential gas flowsis a chemically reactive gas.

Fluidic levitation with radial flow can be used concurrently withdeposition processes to provide a method for thermally isolating themoveable substrate and its surfaces from physical contact with anythermal sinks, thereby enabling effective temperature control for bothheating and cooling—especially during the use of optional processingsteps involving high photon flux radiative exposures such as optionallyradiative curing with either IR or UV radiation. The use of processingsteps involving the use of radiation of all types for the purposes ofstabilizing and inducing further changes in material properties ofdeposited films during pneumatic levitation is specifically contemplatedand such radiation sources may include ionizing radiation sources suchas x-rays, gamma rays, and the like as well as lower photon energyradiation types such as ultraviolet radiation and infrared radiation.The use of microwave radiation for substrate treatment of a microwaveadsorbing substrate is specifically contemplated as applied to thepneumatic levitation of a moveable substrate with a levitationstabilizing structure. The use of induction heating for substratetreatment of a conducting substrate is specifically contemplated asapplied to the pneumatic levitation of a moveable substrate with alevitation stabilizing structure. The rapid radial flow in the volumebetween the moveable support surface with its levitation stabilizationstructure and the gas-emanating stationary support enables excellentcleanliness and low contamination during deposition processes executedat elevated temperatures as well as the capability to induce rapidcooling once heating is discontinued. The effluent fluid from theprocess is optionally managed by the use of a supplemental laminar flowof inert gas around the moveable substrate and stationary support forthe purpose of removing the gaseous process effluent from the regionproximate to the moveable substrate and the stationary support assemblyfor disposal. U.S. Pat. No. 5,370,709 has previously disclosed thermalannealing processes and deposition processes using reactive precursorsby employing pneumatic levitation with a single orifice but theapparatus disclosed therein required the use of physical stops toprevent the substrate from sliding off the “suction plate”. Depositionprocesses employing pneumatic levitation without the use of substratemotion restraining structures such as physical stops on the stationarysupport plate are not contemplated in U.S. Pat. No. 5,370,709.

The drawings in FIG. 15 through FIG. 21 are intended to disclose themethod of compound fluid formation employed in apparatus 20. FIG. 15ashows an isometric view of three concentric fluid delivery tubes: outersheath fluid delivery tube 80, inner coaxial fluid delivery tube 82, andinner coaxial fluid delivery tube 84. FIG. 15a shows an isometric viewof a plurality of axially parallel tubes that have a common axis whereinthe axially parallel tubes are concentric. In an embodiment, apparatus20 includes a plurality of axially parallel tubes that coaxial,concentric, or collinear.

FIG. 15b shows a cross-section of the three coaxial fluid delivery tubes80, 82, and 84. FIG. 15b shows a cross-sectional view of a plurality ofaxially parallel tubes 80, 82, and 84 that have a common axis whereinthe axially parallel tubes are concentric. When fluids are flowingthrough coaxial fluid delivery tubes 80, 82, and 84 all fluids flow inan axially symmetric manner. According to the literature conventionsdisclosed by Hertz and Hermanrud (loc cit), fluids that flow in theinterior of an axially symmetric fluid flow will be called primaryfluids. Fluids that are in contact with and surround the primary fluidas a sheath are called secondary fluids. FIG. 15c shows a cross-sectionof one embodiment of an axially symmetric fluid flow emanating fromcoaxial fluid delivery tube arrangement shown in FIGS. 15a and 15b .FIGS. 15c and 15d show a compositional cross-section of the fluid flowexiting from the coaxial tube arrangement shown in FIG. 15a . FIG. 15cshows that the cross-section of the compound fluid flow emanating fromend of coaxial fluid delivery tubes 80, 82, and 84 in FIG. 15a isspatially non-uniform in composition when a primary fluid 86 flowsthrough tube 84 and a secondary fluid 88 flows through coaxial tubes 80and 82. In another embodiment, when primary fluid 86 flows throughcoaxial fluid delivery tube 82 whilst secondary fluid 88 flows throughcoaxial tubes 80 and 84 the compositional cross-section of the compoundfluid is shown in FIG. 15d . In another embodiment that is not shown,primary fluid 86 flows through coaxial tubes 84 and 82 whilst secondaryfluid 88 flows through tube 80 then the compound fluid flow is similarto FIG. 15c except that the cross-section of the primary fluid islarger. The coaxial arrangement of fluid delivery tubes shown in FIG.15a can be employed with three fluids to form more complicated compoundfluid flows comprised of concentric coaxial compound fluid flows.

Some aspects of FIG. 15 will now be described in more detail for onesimple embodiment of the method of use where the fluid is gaseous. Eachgas delivery tube in FIG. 15a is coaxial with all other gas deliverytubes. The array of coaxial gas delivery tubes in FIG. 15 consists of aplurality of tubes, the cross-sectional shape of each tubes beingarbitrary with the provision that a hollow region exists for gas to flowthrough, and each of the tubes may contain a gas of differingcomposition. The tubes employed in the coaxial array for producing acoaxial compound jet can have a cross-sectional shape of a simplepolygon, convex or concave, with n vertices, where n≥3. As mentionedpreviously, oval and circular shapes are considered polygons with aninfinitely large number of vertices and sides and thus are permissiblefor use in construction of a coaxial tube array. FIG. 15b shows a planview of gas delivery tubes 80, 82, and 84 and the centroids of thepolygonal cross-sectional shape of each gas delivery tube 80, 82, and 84are coincident, thereby demonstrating that gas delivery tubes 80, 82,and 84 are coaxial. Gas delivery tube 80 is in fluid communication witha source of gas A of composition A in such a way that the flow of gas incoaxial gas delivery tubes 82 and 84 does not contact or mix with anyother gas until it reaches the exit orifice of inner coaxial gasdelivery tubes 82 and 84. The gas of composition A is supplied using aflow control mechanism that can utilize either a pressure feedback loop,a flow feedback loop, or a feedback loop utilizing both pressure andflow control of the gas of composition A. A gas A of composition A isthus flowed through outer sheath delivery tube. Inner coaxial gasdelivery tube 82 is in fluid communication with a source of gas B ofcomposition B in such a way that the flow of gas B in tube 82 does notmix with any other gas until it reaches the exit orifice of innercoaxial gas delivery tubes 82 and 84. Inner coaxial gas delivery tube 82is in fluid communication with a source of gas B of composition B insuch a way that the flow of gas B in tube 82 does not mix with any othergas until it reaches the exit orifice of inner coaxial gas deliverytubes 82 and 84. The gas of composition B is supplied using a flowcontrol mechanism that can utilize either a pressure feedback loop, aflow feedback loop, or a feedback loop utilizing both pressure and flowcontrol of the gas of composition B. A gas of composition B is thusflowed through inner coaxial delivery tube 82. Similarly, inner coaxialgas delivery tube 84 is in fluid communication with a source of gas C ofcomposition C in such a way that the flow of gas B in tube 84 does notmix with any other gas until it reaches the exit orifice of innercoaxial gas delivery tubes 82 and 84. Inner coaxial gas delivery tube 84is in fluid communication with a source of gas C of composition C insuch a way that the flow of gas C in tube 84 does not mix with any othergas until it reaches the exit orifice of inner coaxial gas deliverytubes 82 and 84. The gas of composition C is supplied using a flowcontrol mechanism that can utilize either a pressure feedback loop, aflow feedback loop, or a feedback loop utilizing both pressure and flowcontrol of the gas of composition C. A gas of composition C is thusflowed through inner coaxial delivery tube 84.

Gases A, B, and C flowing in coaxial tubes 80, 82, and 84 flow in thesame direction and at the same velocity. It is recognized that the massflow rates of gas A and gas B may differ for the flow velocities of gasA and gas B to match because gas velocity is dependent on thecross-sectional area of the exit orifice for the two gases. It is withinthe scope of the invention that the cross-sectional area of the annulusdefined by inner coaxial gas delivery tube 82 and inner coaxial gasdelivery tube 84 may equal the cross-sectional area of the annularregion located between outer sheath gas delivery tube 80 and innercoaxial gas delivery tube 82. Similarly, it is within the scope of theinvention that the cross-sectional area defined by inner coaxial gasdelivery tube 84 may equal the cross-sectional area of the annularregion located between outer sheath gas delivery tube 80 and innercoaxial gas delivery tube 82. A compound coaxial fluid flow is formed bythe combination of the fluid flow occurring at the exit of inner coaxialgas delivery tubes, 82 and 84. Each fluid flow in the compound coaxialfluid flow is centered on the same fluid flow axis and each fluid flowmay contain a fluid of differing chemical composition. Formation ofcoaxial compound fluid flow is most effective when flow velocities ofgases A, B, and C are limited to regime of flow velocities exhibitinglaminar flow characteristics as is familiar to those skilled in the artof fluid mechanics. Gas dynamic focusing can occur when the flowvelocity of gas A from outer sheath fluid delivery tube 80 is largerthan the gas flow velocity of gas B from coaxial fluid delivery tube 82and also that of gas C from coaxial fluid delivery tube 84. Gas dynamicfocusing can be varied according to the relative gas velocities of gasA, B, and C.

The coaxial compound fluid flow delivery assembly 90 shown in FIG. 16provides a more complete understanding of the use of the coaxial fluiddelivery tube arrangement of FIG. 15a in compound jet forming apparatus20. Coaxial fluid delivery tubes 80, 82, and 84 are in fluidcommunication with valves 92, 96, and 94 respectively. Valves 94 and 96are three way controllable valves in fluid communication with reactivefluid inlet 116 and chemically inert fluid inlet 118. Valve 92 is influid communication with inert fluid inlet 118 and 2 way valve 92controls the supply of chemically inert secondary fluid to the coaxialcompound fluid exiting from coaxial fluid delivery tubes 80. Theswitchable valves 94 and 96 determine the location of the chemicallyreactive primary fluid in the coaxial compound fluid flow exitingcoaxial fluid delivery tubes 80, 82, and 84. When switchable valve 94allows fluid communication between reactive fluid inlet 116 and coaxialfluid delivery tube 84, then the primary fluid flows through coaxialfluid delivery tube 84 and when the remaining coaxial fluid deliverytubes 80 and 82 are in fluid communication with and flowing chemicallyinert fluid then the exiting compound fluid flow has a compositionalcross-section shown in FIG. 15c . Similarly in another embodiment, whenswitchable valve 96 allows fluid communication between reactive fluidinlet 116 and coaxial fluid delivery tube 86 when the remaining coaxialfluid delivery tubes 80 and 84 are in fluid communication with andflowing chemically inert fluid, then the chemically reactive primaryfluid flows in the annular volume between coaxial fluid delivery tubes84 and 82 and the exiting compound fluid flow has a compositionalcross-section shown in FIG. 15d . In both configurations chemicallyinert secondary fluid flows in the annular volume between coaxial fluiddelivery tubes 80 and 82. In another embodiment of apparatus 20, thecoaxial compound fluid flow delivery assembly of FIG. 16 has coaxialfluid delivery tube 80 extended beyond coaxial fluid delivery tubes 84and 82 and connected directly to fluid collimating conduit 14 of thestationary fluid emitting support through which fluid will flow throughoutlet 19 of apparatus 20. In an additional embodiment, the internaldiameter of coaxial fluid delivery tube 80 extended beyond coaxial fluiddelivery tubes 84 and 82 is reduced in a smooth and monotonic fashion orthe outlet 19 of apparatus 20 is reduced in a smooth and monotonicfashion to match the internal diameter of fluid collimating conduit 14thereby providing a way of hydrodynamically focusing the coaxialcompound fluid prior to formation of the coaxial compound jet emanatingfrom fluid collimating conduit 14 in the stationary fluid emittingsupport.

Some aspects of FIG. 16 will now be discussed in further detail. Thecoaxial compound fluid flow delivery assembly 90 may optionally containheating elements to control the temperatures of the fluids flowingthrough assembly 90. It is advantageous in some applications to controlthe gas composition flowing from the exit port of a compound fluid flowor a compound coaxial fluid flow. In order to control the finalcomposition of the fluid flow a means for temporally varying the gascomposition in one or more of the gas flows making up the compound jetsuch as a valve is employed. FIG. 16 shows a structure for producing acoaxial compound jet with varying composition by changing thecomposition of gas flowing through two coaxial fluid delivery tubes, 82and 84, whose composition can be changed according to a pre-determinedtimed sequence.

In one embodiment, all gas flowing through the outer sheath gas deliverytube 80 and coaxial gas delivery tubes 82 and 84 is the same chemicalcomposition. Preferably the initial composition of the gas flowing inthe assembly comprised of elements 80, 82, and 84 is an inert gas suchas nitrogen or argon. The composition of the gas flowing through coaxialgas delivery tube 82 is switched to a different composition containing achemically reactive species by switching a valve 96 so that thechemically reactive fluid flows through coaxial gas delivery tube 82 fora period of time, after which the gas flowing through coaxial gasdelivery tube 82 is switched back to inert gas. After a predefined timeperiod, a valve 94 attached to coaxial gas delivery tube 84 is switchedto allow a gas mixture containing a second different chemically reactivefluid to flow through coaxial gas delivery tube 84 for a set period oftime after which time the gas composition in coaxial gas delivery tube84 is switched back to inert gas. The timed sequence described is thegas exposure sequence that is similar to the timed fluid exposuresequence employed in many atomic layer deposition processes. In oneembodiment, the use of the coaxial compound fluid flow delivery assembly90 in apparatus 20 is a method of controlling the fluid flow totemporally intersperse single-fluid flows with a fluid flow having twoor more fluids. In one embodiment, all gases are delivered to themoveable substrate through the use of a coaxial compound jet producedusing elements 80, 82, and 84 that is employed to pneumatically levitatea moveable substrate by Bernoulli levitation through the use of a singleorthogonal jet emanating from a stationary support that impinges on amoveable substrate in an orthogonal manner. The moveable substrate mayhave a levitation stabilizing structure on the opposing surface facingthe orthogonal jet, thereby providing stable pneumatic levitationconditions during processing. The use of three way valves as shown inassembly 90 of FIG. 16 can be particularly advantageous when thecomposition of the gas in a gas delivery tube, like for example acoaxial gas delivery tube 82 or coaxial gas delivery tube 84, isfrequently changed between an inert fluid and a gas chemically reactivefluid containing, for example, chemically reactive molecules.

It is preferred that the chemical composition of the outer most layer ofthe coaxial jet that is produced by fluid flowing through the annularregions between outer sheath gas delivery tube 80 and inner coaxial gasdelivery tube 82 be a chemically unreactive fluid in the gaseous statesuch as argon or nitrogen. Assembly 90 shown in FIG. 16 has theadvantage of using a coaxial jet structure to provide a physical barrierof non-reactive gaseous fluid material on the outside of the jet throughwhich the reactive chemicals in the collinear jet must pass beforecontacting a surface such as the interior surface a piece of tubing orthe interior surface of a fluid collimating conduit, bore or orifice inthe stationary support.

The advantage to using coaxial compound jets and variants thereof, as away of producing, transporting and delivering a gas flow containing areactive gas mixture to the stationary support, is to prevent andminimize contact of reactive chemical materials in the jet with thesidewalls of the fluid collimating conduits, orifices, bores, andnozzles in the stationary support plate, thereby avoiding chemicalcontamination of the fluid collimating conduits in the stationary plate.It is particularly advantageous to have the outermost gas compositionwhich is also called the sheath of a compound fluid flow comprised of anessentially inert, chemically unreactive gas such as argon or nitrogenso that reactive chemicals can only contact the sidewalls, nozzles,bores, fluid collimating conduits, and orifices of the stationarysupport and associated fluid delivery tubing using sideways gaseousdiffusion. For example, if coaxial fluid flow comprised of a centerchemical composition containing water vapor surrounded by a nitrogensheath is prepared then the water will not only travel collinearly andcoaxially with the nitrogen flow but it will also begin to diffuseradially outward along the radius of the jet. The diffusion coefficientfor water in nitrogen at room temperature is between 0.2 and 0.3 cm² atmsec⁻¹ and the diffusion along the radius of the jet is much slower thanthe transport speed of water in nitrogen along the fluid flow directionfor fluid flows usually employed in substrate processing, therebylimiting potential contamination of the internal surfaces of theapparatus chemical delivery system.

Further clarification of the disclosed inventive method of fluidiclevitation is furnished the embodiment of an apparatus for fluidiclevitation of a moveable substrate with levitation stabilizing structureshown in FIG. 17. FIG. 17 is a cross-sectional view illustrating anembodiment of the present inventive method for practicing fluidiclevitation with chemically reactive species wherein the preferred fluidis a gaseous fluid. FIG. 17 shows a moveable substrate 10 with alevitation stabilizing structure 30 fabricated thereupon where thesurface of moveable substrate 10 with the levitation stabilizingstructure 30 opposes the gas emanating surface of stationary supportthrough which fluid will flow using fluid collimating conduit 14. Fluidcollimating conduit 14 is in fluid communication with a pressurizedfluidic source emanating from an apparatus for production of compoundfluid flows and jets 20 which is, in turn, in fluid communication withnon-reactive gas inlet 118 and reactive gas inlet 116 through valves 92,94, and 96.

FIG. 17 illustrates the appropriate relative positions of the elementsmoveable substrate 10 with levitation stabilizing structure 30 relativeto the stationary support 12 and fluid collimating conduit 14 for theuse of levitation stabilizing structure 30 to be effective as a methodof positional stabilization during fluidic levitation with an orthogonaljet emanating from fluid collimating conduit 14. It has been found thatthe use of the levitation stabilizing structure as a method forimproving the lateral stability of a moveable substrate during pneumaticlevitation only requires that the fluid jet from jet forming fluidcollimating conduit 14 of stationary support 12 through which fluid willflow and impinge on the surface of moveable substrate 10 within theinterior impingement area defined by the surface bounded and enclosed bythe walls of the levitation stabilizing structure 30 fabricated on thesurface of moveable substrate 10. It is preferred that the fluid jetfrom jet forming fluid collimating conduit 14 of stationary fluidemitting support 12 impinge on the surface of moveable substrate 10 nearthe centroid of interior impingement area defined by the area enclosedby the interior walls of the levitation stabilizing structure 30fabricated on the surface of moveable substrate 10. It is preferablethat the centroid of the interior impingement area enclosed by theinterior walls of the levitation stabilizing structure 30 fabricated onthe surface of moveable substrate 10 be located within the impingementarea enclosed by the interior walls of the levitation stabilizingstructure 30. The fluid collimating conduit on the stationary fluidemitting support is an alignment feature on the surface of thestationary fluid emanating support and the centroid of the interiorimpingement area of the levitation stabilizing structure is aligned withthe alignment feature wherein the alignment feature is a fluidcollimating conduit on the surface of the stationary fluid emanatingsupport. Thus, according to the first three steps of the processsequence disclosed in FIG. 14 the method for fluidic levitationcomprises the steps of:

1. providing a substrate with a levitation stabilizing structure on asurface of a substrate and positioning said substrate proximate to afluid emitting surface of a stationary fluid emanating support throughwhich fluid will flow in a conformal-wise manner with the levitationstabilizing structure overlaying the surface of the substrate and facingthe stationary fluid emanating surface;

2. initiating at least one collimated fluid flow from the stationaryfluid emanating support surface through which fluid will flow to producea collimated fluid jet; and

3. controlling the collimated fluid flow emanating from the stationaryfluid emanating support through which fluid will flow to fluidicallylevitate the substrate and levitation stabilizing structure proximate tothe surface of the stationary fluid emanating support.

It has been observed experimentally that the alignment of the centroidof the interior impingement area of the levitation stabilizing structurewith at least one alignment feature on the surface of the stationaryfluid emanating support is not highly critical as the levitationstabilizing structure exhibits self-alignment during the levitationprocess. The reasons for self-aligning behavior during pneumaticlevitation are described in more detail below. This is a distinctadvantage of using a levitation stabilizing structure during pneumaticlevitation.

FIG. 17 also shows an embodiment of an apparatus 20 for production ofcompound fluid flows and jets. The compound fluid flow forming apparatus20 is comprised of multiple elements including at least one coaxialcompound fluid flow delivery assembly 90 as shown in FIG. 16 andadditional means for controlling the temperature, pressure, and flow ofat least one fluid. The additional means for controlling thetemperature, pressure, and flow of at least one fluid of compound fluidforming apparatus 20 are not shown in FIG. 20.

The coaxial compound fluid flow delivery assembly 90 in FIG. 17 iscomprised of coaxial fluid delivery tubes 80, 82 and 84 and valves 92,94, and 96 and provides a means for controlling the composition of thecompound fluid flow. The compound fluid forming apparatus 20 shown inFIG. 17 has at least two inlets. Inlet 116 allows a first reactive fluidto flow into apparatus 20 and inlet 118 allows a second non-reactivefluid to flow into apparatus 20. Apparatus 20 has a fluid outlet 19 influid communication with fluid collimating conduit 14. Fluid outlet 19may also serve as a means to focus the compound fluid flow usinghydrodynamic methods prior to formation of a compound coaxial jetemanating from fluid collimating conduit 14. The function of apparatus20 is to combine at least 2 fluid flows, a first fluid flow and a secondfluid flow, to form a compositionally segregated compound fluid flowexiting apparatus 20 through outlet 19 and flowing though fluidcollimating conduit 14 of the stationary fluid emitting support. In oneembodiment the first fluid flow can be a reactive fluid and the secondfluid flow can be a non-reactive fluid. Unlike any of the prior artutilizing fluid flows for fluidic levitation, the compound fluid flowexiting apparatus 20 at fluid outlet 19 is a spatially non-uniformcomposition of matter in at least one dimension comprised of achemically reactive fluid flow encased and surrounded by a chemicallynon-reactive fluid flow. A spatially non-uniform composition of matteris a composition of matter whose chemical composition changes dependingon the sampling location with the composition of matter volume. Thecompound fluid flow emanating from outlet 19 of apparatus 20 is injectedthrough fluid collimating conduit 14 to form a spatially non-uniformcompound jet that can be made non-reactive with the critical fluidcontact regions of the fluid delivery system employed for fluidiclevitation.

The compound fluid forming apparatus 20 optionally includes means foraccurately controlling the temperature, pressure, and flow of the fluidsthat are employed for the purpose of producing a collimated compoundfluid jet. Typical means for controlling pressure of gaseous and liquidfluids include both passively and actively controlled pressureregulators including electronically controlled pressure regulators andother types of pressure regulator methods known in the art. Typicalmeans for controlling the temperature of a fluid include passive andactively controlled heating and cooling units including heat exchangers,heating tapes and coils as well as cooling coils through which the fluidpasses, temperature controlled reservoirs, and other devices known tothose skilled in the art of temperature control of fluids. Temperatureand pressure control loops employed to achieve stable fluid temperaturesand fluid pressures may incorporate the use automated temperature andpressure control units. Typical means for controlling the flow of one ormore gaseous fluids include the use of orifices of known diameter withknown pressure-flow relationships, gas flow meters, flow controllers,control valves, and variable control valves of all types including massflow meters and mass flow controllers, rotameters, Coriolis flow meterscoupled with flow controllers, turbine flow meters, pitot based flowmeters and other types of fluid flow meters familiar to those skilled inthe art of process control of flowing fluid media where the fluid is aliquid or a gas.

Controlling the fluid composition is an important feature of theapparatus. For example, specific valve configurations can be employed inapparatus 20 to allow the apparatus 20 to produce compound jets whosespatially non-uniform composition can be varied as a function of time asthe compound fluid flows through fluid collimating conduit 14. This is adistinct advantage because it allows the surface of moveable substrate10 that opposes the stationary fluid emitting support to be exposed to achemically reactive fluid with a known amount of chemically reactivespecies for a known amount of time. Exposure of a surface to achemically reactive species for a known amount of time is also known assurface exposure or surface dosing and an apparatus that provides ameans to dose a surface with a specific reactive fluid flow is extremelyuseful.

It is further recognized that the entire assembly represented by thecross-sectional view of FIG. 17 could be rotated by 180 around an axisnormal to the plane of FIG. 17 and the positional configuration willstill be functional. The use of a levitation stabilizing structure 30during fluidic levitation does not alter the function of a fluidiclevitation apparatus employing Bernoulli airflow with respect tophysical orientation of the apparatus, and in fact improves therobustness of fluidic levitation with respect to tilting of thegas-emanating stationary support through which fluid will flowregardless of the apparatus attitude and orientation. Fluidic levitationcan take place when the velocity vector of the orthogonal fluid jet isessentially parallel to the gravitational force vector or when thevelocity vector of the orthogonal fluid jet is essentially anti-parallelto the gravitational force vector. The presence of a levitationstabilizing structure 30 on the moveable substrate surface does notalter the relationships between the pneumatic forces that are generatedby the fluid flow from the orthogonal jet that flows between thesubstrate surface and the fluid emitting support surface and thegravitational force vector that are inherently present in fluidiclevitation processes employing Bernoulli airflow. This is a distinctadvantage of the invention.

As was previously disclosed in FIG. 13, it is also recognized that thestationary support through which fluid will flow employed for fluidiclevitation is not restricted to a planar configuration as illustrated inFIG. 17. The features of the stationary support comprise the following:the stationary fluid emitting support contains at least one fluidcollimating conduit in fluid communication with a manifold and apressurized fluid source, said fluid collimating conduit having across-sectional area less than or equal to ¼ of the surface area of theinterior impingement area of the levitation stabilizing structure; thesurface area of the stationary fluid emitting support is at least equalto the surface area of the interior impingement area on the moveablesubstrate; and the fluid flow between the stationary support and themoveable substrate is characterized by radial flow patterns that areessentially symmetric with respect to the centroid of the interiorimpingement area. It is preferred that said fluid collimating conduithave a cross-sectional area less than or equal to ¼ of the impingementarea enclosed by the walls of the levitation stabilizing structure.

The function of the levitation stabilizing structure, also referred toas the LSS, fabricated on the moveable substrate surface is to harnessthe inherent kinetic energy of the gaseous compound fluid jet flow andof the resultant fluidic layer employed in fluidic levitation so as toconvert said kinetic energy into directional forces for the purpose ofintroducing positionally restorative forces that act in a restorativemanner to control and minimize undesirable lateral movement of themoveable substrate during fluidic levitation.

The symmetric radially outward flow which occurs during pneumaticlevitation processes employing one or more orthogonal compound jets canthus be harnessed to achieve positional stability of a pneumaticallylevitated moveable substrate using a levitation stabilizing structurefabricated on the opposing surface of the moveable substrate.Furthermore, the fluid flow from one or a plurality of orthogonal ortilted compound jets contains substantial pneumatic energy in the formof both kinetic and potential energy and this unharnessed pneumaticenergy can be used to achieve positional stability of a pneumaticallylevitated moveable substrate.

Positional stability of the moveable substrate during pneumaticlevitation is achieved most readily when the stationary fluid emittingsupport contains fluid collimating conduits used for the generation offluid jets—tilted or orthogonal, compound or single—that impinge withinthe interior impingement area on the surface of the opposing moveablesubstrate that is within the confines of the area enclosed by the wallsof the levitation stabilizing structure that is located on and incontact with the moveable substrate surface that opposes and faces thestationary gas emitting support surface, as shown in FIG. 17. Thelocation of the levitation stabilizing structure on the moveablesubstrate is a feature that distinguishes the inventive method from allother previous attempts to address positional stability during pneumaticlevitation. Furthermore, the inventive method is not restricted toplanar plate-like substrates although planar substrates are preferred.Additionally, the use of compound jets during fluidic levitation is adistinguishing feature of the inventive method from all other previousattempts to address delivery of chemically reactive fluids duringfluidic levitation.

FIG. 18 discloses another embodiment of the method of compound fluidflow formation employed in apparatus 20. FIG. 18a shows an isometricview of three fluid delivery tubes: an outer sheath fluid delivery tube80 and an array of two parallel collinear fluid delivery tubes 110. FIG.18a shows an isometric view of an assembly of collinear fluid deliverytubes that can be incorporated into apparatus 20 for the purposes ofproducing a compound collinear fluid flow and the structure of 18 a forproviding a compound collinear fluid flow is comprised of an outersheath gas delivery tube 80 and an array of collinear parallel gasdelivery tubes 110. The array of collinear parallel gas delivery tubes110 consists of a plurality of parallel tubes, the cross-sectional shapeof each tubes being arbitrary with the provision that a hollow regionexists for gas to flow through, and each of the tubes may contain a gasof differing composition. Thus, in an embodiment, the compound-gas-jetstructure includes a plurality of axially parallel tubes.

The tubes employed in the array structure 110 for producing a collinearjet can have a cross-sectional shape of a simple polygon, convex orconcave, with n vertices, where n≥3. As mentioned previously, oval andcircular shapes are considered polygons with an infinitely large numberof vertices and sides and thus are permissible for use in constructionof parallel tube array 110. Each gas delivery tube in FIG. 18a is inindividual fluid communication with its own gas source and flow controlmechanism such that the flow of gas in each tube of FIG. 18a , includingthe outer sheath gas delivery tube 80, does not mix with any other gasuntil it reaches the exit orifice gas delivery tube array 110. FIG. 18bshows a plan view of the structure disclosed in FIG. 18a for producing acompound collinear fluid flow from apparatus 20 and contains outersheath gas delivery tube 80 and inner array of collinear parallel gasdelivery tubes 110. Each gas delivery tube in the collinear fluiddelivery tube array 110 can be considered a fluid injection tube orfluid delivery tube whose fluid composition can be changed as desiredusing, for example, a switchable 3 way valve that is in fluidcommunication with two fluids of two different compositions.

FIG. 18b shows a cross-section of the three fluid delivery tubescomprised of outer sheath fluid delivery tube 80 and the two polygonalcollinear fluid delivery tubes 112 and 114 that comprise the array 110of parallel collinear fluid delivery tubes. The two collinear fluiddelivery tubes 112 and 114 are shown having a circular shape in FIG. 18b. When fluids are flowing through fluid delivery tubes 80, 112, and 114it is clear that fluids flowing through fluid delivery tubes 112 and 114of array 110 are not flowing coaxially. Fluids flowing through fluiddelivery tubes 112 and 114 of array 110 are flowing in a collinearfashion parallel to the central axis of outer sheath fluid delivery tube80. The spatial distribution of composition produced in the compoundfluid flow emanating from the arrangement of fluid delivery tubes shownin FIGS. 18a and 18b is collinear with the axis of the outermost fluiddelivery tube and in this disclosure is called a collinear compoundfluid flow. The collinear arrangement of fluid flows distinguishescollinear compound fluid flow from coaxial compound fluid flow. In thisdisclosure collinear compound fluid flows will be referred to accordingto the literature conventions established by Hertz and Hermanrud (loccit), fluids that flow in the interior of a compound fluid flow will becalled primary fluids. Fluids that are in contact with and surroundedthe primary fluid as a sheath are called secondary fluids. FIG. 18cshows a compositional cross-section of one possible embodiment of acollinear compound fluid flow emanating from the collinear compoundfluid delivery tube arrangement shown in FIGS. 18a and 18b . FIG. 18cshows that the cross-section of the compound fluid flow emanating fromend of collinear fluid delivery tubes 80, 112, and 114 in FIG. 18a isspatially non-uniform and non-axially symmetric in composition when aprimary fluid 86 flows through tube 112 and secondary fluid 88 flowsthrough coaxial tubes 80 and 114. FIG. 18d shows that the cross-sectionof the compound fluid flow emanating from end of collinear fluiddelivery tubes 80, 112, and 114 in FIG. 18a is spatially non-uniform incomposition when a primary fluid 86 flows through collinear fluiddelivery tubes 112 and 114 and secondary fluid 88 flows through coaxialtubes 80. The collinear arrangement of fluid delivery tubes shown inFIGS. 18a and 18b can be expanded to employ three or more fluids to formmore complicated compound fluid flows comprised of three or morecollinear compound fluid flows.

The compound collinear fluid flow delivery assembly 120 shown in FIG. 19provides a more complete understanding of the use of the collinear fluiddelivery tube arrangement of FIG. 18a in compound jet forming apparatus20. Collinear fluid delivery tubes 80, 112, and 114 are in fluidcommunication with valves 92, 96, and 94 respectively. Valves 94 and 96are three way controllable valves in fluid communication with reactivefluid inlet 116 and chemically inert fluid inlet 118. Valve 92 is influid communication with inert fluid inlet 118 and 2 way valve 92controls the supply of chemically inert secondary fluid 88 to thecollinear compound fluid flowing through collinear fluid delivery tube80. The fluid inlets 116 and 118 are in fluid communication withpressurized-gas sources containing chemically reactive and chemicallynon-reactive gasses, respectively. The switchable valves 94 and 96determine the location of the chemically reactive primary fluid in thecollinear compound fluid flow exiting collinear fluid delivery tubes 80,112, and 114. When switchable valve 94 allows fluid communicationbetween reactive fluid inlet 116 and collinear fluid delivery tube 114,then the primary fluid flows through collinear fluid delivery tube 114and the exiting compound fluid flow has a compositional cross-sectionequivalent to that shown in FIG. 18c . Similarly in another embodiment,when switchable valve 96 allows fluid communication between reactivefluid inlet 116 and collinear fluid delivery tube 112 and the chemicallyreactive primary fluid flows through collinear fluid delivery tube 112the exiting compound fluid flow has a compositional cross-sectionequivalent to that shown in FIG. 18c . In both configurations chemicallyinert secondary fluid flows in the volume between outer sheath fluiddelivery tube 80 and collinear fluid delivery tubes 112 and 114. Inanother embodiment of apparatus 20, the compound collinear fluid flowdelivery assembly 120 of FIG. 19 has outer sheath fluid delivery tube 80extended beyond collinear fluid delivery tubes 114 and 112 and connecteddirectly to fluid collimating conduit 14 of the stationary fluidemitting support by outlet 19 of apparatus 20. In an additionalembodiment, the internal diameter of outer sheath fluid delivery tube 80extended beyond collinear fluid delivery tubes 114 and 112 is reduced ina smooth and monotonic fashion or the outlet 19 of apparatus 20 isreduced in a smooth and monotonic fashion to match the internal diameterof fluid collimating conduit 14 thereby providing a way ofhydrodynamically focusing the collinear compound fluid flow prior toformation of the collinear compound jet emanating from fluid collimatingconduit 14 in the stationary fluid emitting support through which fluidwill flow. In apparatus 20, the fluid outlet 19 that is in fluidcommunication with fluid collimating conduit 14 can be convergent ordivergent, depending on whether the diameter of fluid collimatingconduit 14 is larger or smaller than the inner diameter of fluid outlet19. Regardless of the differences in diameter between fluid collimatingconduit 14 and outlet 19, it is desirable that the diameter of the twoelements 14 and 19 equal at the point of fluid connection between thetwo elements 14 and 19. Thus, in one embodiment fluid outlet 19 ismonotonically convergent between apparatus 20 and fluid collimatingconduit 14 to enable matched interior diameters at the fluidcommunication junction of apparatus 20 with fluid outlet 19 and toenable matched interior diameters at the fluid communication junction offluid outlet 19 and fluid collimating conduit 14. In one embodiment, theuse of the collinear compound fluid flow delivery assembly 120 inapparatus 20 is a method of controlling the fluid flow to temporallyintersperse single-fluid flows with a fluid flow having two or morefluids.

FIG. 20 discloses another embodiment of the method of compound fluidformation employed in apparatus 20. FIG. 20a shows an isometric view ofan array of collinear fluid delivery tubes 130 where at least oneadditional collinear fluid delivery tube has been added to array 110 oftwo collinear fluid delivery tubes 112 and 114 shown in FIG. 18. FIG.20b shows an isometric view of an embodiment of the modified collinearfluid delivery tube arrangement comprised of multiple collinear fluiddelivery tubes surrounded and enclosed by an outer sheath fluid deliverytube 80. FIG. 20b shows outer sheath fluid delivery tube 80 and an arrayof ten parallel collinear fluid delivery tubes 130. The internaldiameters of the collinear fluid delivery tubes in array 130 can be thesame or the internal diameters of the collinear fluid delivery tubes inarray 130 can be different. Alternatively, the internal diameter of thecollinear fluid delivery tubes in array 130 can be a selection of tubes,some of which have identical internal diameters and some of which havedifferent internal diameters.

FIG. 20c shows a cross-section of the modified collinear fluid deliverytube arrangement comprised of outer sheath fluid delivery tube 80 and anarray of ten collinear fluid delivery tubes 130 that is surrounded andenclosed by outer sheath fluid delivery tube 80. The cross-sectionalimage of FIG. 20c shows a dotted hexagonal outline 98 that defines oneembodiment of the arrangement of collinear fluid delivery tubes in array130. Referring to FIG. 20c , each vertex of the dotted hexagonal outlinecoincides with the center of a tube in the modified collinear fluiddelivery tube array 130. In the embodiment of the modified collinearfluid delivery tube arrangement shown in FIG. 20c the cross-sectionalarrangement of the collinear fluid delivery tubes in collinear fluiddelivery tube array 130 is based on hexagonally close packed array;however, it is recognized that other packing arrangements of fluiddelivery tubes in the collinear fluid delivery tube array are possibleand can be preferred for some applications. For example, in an alternateembodiment the array of collinear tubes are arranged in a packed arraywhere the cross-sectional view of the arrangement of the packed arrayshows that each tube occupies the vertex of a square or some otherregular planar polygon. In some applications it can be preferable tohave the collinear fluid delivery tubes of array 130 arranged randomlywithin the cross-sectional area of the outer fluid delivery tube 80.FIG. 20c shows a hexagonal arrangement of gas delivery tubes 130 asindicated by hexagonal outline 98 indicating a hexagonal tube arrayaround located around collinear injection tube 112. Collinear fluiddelivery tube 112 is located at the center of the hexagonal arrayoutline 98 and a second collinear fluid delivery tube 114 is identifiedthat is adjacent to collinear injection tube 112. FIG. 20c shows aninner array of collinear parallel gas delivery tubes 130 encompassed andsurrounded by outer sheath gas delivery tube 80. Each gas delivery tubein the collinear parallel gas delivery tube array 130 can be considereda fluid delivery tube whose fluid composition can be changed as desiredusing, for example, a switchable 3 way valve that is in fluidcommunication with two fluids of two different compositions.

Referring to FIG. 20, the array of collinear parallel gas delivery tubes130 consists of a plurality of axially parallel tubes, thecross-sectional shape of each of the tubes being arbitrary with theprovision that a hollow region exists for gas to flow through, and eachof the tubes may contain a gas of differing composition. The tubesemployed in the array structure 130 for producing a collinear jet canhave a cross-sectional shape of a simple polygon, convex or concave,with n vertices, where n≥3. As mentioned previously, oval and circularshapes are considered polygons with an infinitely large number ofvertices and sides and thus are permissible for use in construction ofparallel tube array 130.

Referring again to FIG. 20c a method for use of the modified collinearfluid delivery tube arrangement shown in FIG. 20c will be described.When the fluid flow in outer sheath fluid delivery tube 80 and collinearfluid delivery tube array 130 is comprised of fluids with identicalchemical composition, then a fluid flow of uniform chemical compositioncan be formed from the modified collinear fluid delivery tubearrangement shown in FIG. 20 c.

When fluids are flowing through fluid delivery tubes 80, and 112, and114 of array 130 it is clear that fluids flowing through fluid deliverytubes 112 and 114 of array 130 are not flowing coaxially with respect tothe fluid flow from the outer sheath fluid delivery tube 80. Fluidsflowing through fluid delivery tubes 112 and 114 of array 130 areflowing in a collinear fashion parallel to but not concentric with thecentral axis of outer sheath fluid delivery tube 80. The spatialdistribution of composition produced in the compound flow emanating fromthe arrangement of fluid delivery tubes is similar to that shown inFIGS. 18a and 18b and is collinear with the axis of the outermost fluiddelivery tube and in this disclosure is called a collinear compoundfluid flow. The collinear arrangement of fluid flows distinguishescollinear compound fluid flow from coaxial compound fluid flow. In thisdisclosure collinear compound fluid flows will be referred to accordingto the literature conventions established by Hertz and Hermanrud (loccit), fluids that flow in the interior of a compound fluid flow will becalled primary fluids. Fluids that are in contact with and surround theprimary fluid as a sheath are called secondary fluids. The collineararray 130 of fluid delivery tubes shown in FIG. 20 can be employed withthree or more fluids to form more complicated compound fluid flowscomprised of three or more collinear compound fluid flows. A collinearcompound fluid flow can be formed by changing the fluid composition ofthe fluid flowing through one of the fluid delivery tubes in thecollinear fluid delivery tube array 130. In one embodiment, a chemicallyreactive fluid flows through collinear fluid delivery tube 112 whilstall other tubes in the collinear fluid delivery tube array 130 have achemically inert fluid flowing through them. The chemically reactivefluid flowing through collinear fluid delivery tube 112 is the primaryfluid of the compound fluid flow and the secondary fluid of the compoundfluid flow is furnished by the combination of all other fluid flows fromthe remaining nine collinear fluid delivery tubes in array 130 and thefluid flow from the outer sheath fluid delivery tube 80. In anotherembodiment, a chemically reactive fluid flows through collinear fluiddelivery tube 114 whilst all other tubes in the collinear fluid deliverytube array 130 have a chemically inert fluid flowing through them. Thechemically reactive fluid flowing through collinear fluid delivery tube114 is the primary fluid of the compound fluid flow and the secondaryfluid of the compound fluid flow is furnished by the combination of allother fluid flows from the remaining nine collinear fluid delivery tubesin array 130 and the fluid flow from the outer sheath fluid deliverytube 80. In a third embodiment, a chemically reactive fluid flowsthrough collinear fluid delivery tubes 112 and 114 whilst all othertubes in the collinear fluid delivery tube array 130 have a chemicallyinert fluid flowing through them. The chemically reactive fluid flowingthrough collinear fluid delivery tubes 112 and 114 is the primary fluidof the compound fluid flow and the secondary fluid of the compound fluidflow is furnished by the combination of all other fluid flows from theremaining nine collinear fluid delivery tubes in array 130 and the fluidflow from the outer sheath fluid delivery tube 80. The modifiedcollinear fluid delivery tube arrangement shown in FIG. 20c thusprovides a means for producing a plethora of different types of compoundfluid flows the number of which is determined by the number of possiblecombinations of fluids that flow through the various tubes in the array.In array 130 there are, for example, 100 different ways to arrange theflow of two different fluids in the 10 collinear fluid delivery tubes,suggesting multiple opportunities for optimizing a compound fluid flowto maximize delivery of a chemically reactive primary fluid whilereducing chemical contamination of the fluid delivery system bymaximizing the effectiveness of the secondary fluid of the compoundfluid flow. This is a distinctive and inventive feature of the modifiedcollinear fluid delivery tube arrangement. Array 130 also functions as ameans to ensure laminar flow in the compound flow. This is a seconddistinctive and inventive feature of the modified collinear fluiddelivery tube arrangement. In one embodiment the collinear fluiddelivery tube array 130 can be substituted for the array of parallelfluid delivery tubes 110 shown in FIG. 19 thereby resulting in amodified collinear compound fluid flow delivery assembly that is usefulfor fluidic levitation.

It is preferred that the chemical composition flowing through volumebetween the outer sheath gas delivery tube 80 and the array of parallelgas delivery tubes 130 be a chemically unreactive fluid in the gaseousstate such as argon or nitrogen. In one embodiment, flow straighteningtubes in volume between the outer sheath gas delivery tube 80 and thearray of parallel gas delivery tubes 130 are used to ensure laminar flowof a chemically unreactive fluid in the volume between the outer sheathgas delivery tube 80 and the array of parallel gas delivery tubes 130.When a chemically unreactive fluid is flowing through volume between theouter sheath gas delivery tube 80 and the array of parallel gas deliverytubes 130 then the structure shown in FIGS. 20a, 20b, and 20c manifeststhe advantage of producing a fluid flow with a collinear compoundstructure that provide a physical barrier on the outside of the jetthrough which the reactive chemicals from the interior of the collinearfluid flow must pass before contacting a surface of the fluid deliverysystem such as the interior surface a piece of tubing or the interiorsurface of a fluid collimating conduit in the stationary support throughwhich fluid will flow.

The advantage to using collinear compound fluid flow and variantsthereof, as a way of producing, transporting, and delivering a gas flowcontaining a reactive gas mixture to the stationary support, is toprevent and minimize contact of reactive chemical materials in the jetwith the sidewalls of the fluid collimating conduits, orifices, bores,and nozzles in the stationary support plate, thereby avoiding chemicalcontamination of the fluid collimating conduits, orifices, bores, andnozzles in the stationary support. It is particularly advantageous tohave the outermost sheath of a collinear compound fluid flow comprisedof an essentially inert, chemically unreactive gas such as argon ornitrogen so that reactive chemicals can only contact the sidewalls,nozzles, bores, fluid collimating conduits, and orifices of thestationary support and associated fluid delivery tubing using sidewaysgaseous diffusion. For example, if collinear fluid flow comprised of aninner collinear fluid flow of water vapor in surrounding nitrogen sheathis prepared then the water will not only travel collinearly andcoaxially with the nitrogen flow but it will also begin to diffuseradially outward along the radius of the jet. The diffusion coefficientfor water in nitrogen at room temperature is between 0.2 and 0.3 cm² atmsec⁻¹ and at the fluid velocity normally employed in substrateprocessing, this diffusion along the radius of the fluid flow and normalto the direction of fluid flow (normal to the stream line) is muchslower than the transport speed of water in nitrogen along the fluidflow direction (along the stream line), thereby limiting potentialcontamination of the internal walls of the apparatus.

The use of the structure shown in FIG. 20c for generating a collinearjet will now be described for the purposes of pneumatic levitation withvariable gas compositions. Initially, all gas flowing through the outersheath gas delivery tube 80 and the array of parallel gas delivery tubes130 is the same chemical composition. Preferably the initial compositionof the gas flowing in the assembly comprised of elements 80 and 130 isan inert gas such as nitrogen or argon. The composition of the gasflowing through collinear fluid delivery tube 112 in element 130 ischanged to a different chemical composition by switching of a valve sothat chemically reactive fluid flows through collinear fluid deliverytube 112 for a period of time, after which the gas flowing throughcollinear fluid delivery tube 112 is switched back to inert gas. After apredefined time period, a valve attached to collinear fluid deliverytube 114 is switched to allow a chemically reactive fluid to flowthrough collinear fluid delivery tube 114 for a set period of time afterwhich time the gas composition in collinear fluid delivery tube 114 isswitched back to inert gas. The timed sequence described is the gasexposure sequence that is similar to that employed in many atomic layerdeposition processes for monolayer formation on a substrate surface. Inone embodiment, all gases are delivered to the moveable substratethrough the use of a collinear compound fluid flow produced usingelements 80 and 130 as part of apparatus 20 that is employed to furnishthe fluid flow employed to pneumatically levitate a moveable substrateby Bernoulli levitation through the use of a single orthogonal jetemanating from stationary support 12 through which fluid will flow thatimpinges on a moveable substrate 10 in an orthogonal manner. Themoveable substrate 10 may have a levitation stabilizing structure on theopposing surface facing the orthogonal jet, thereby providing stablepneumatic levitation conditions during processing. The use of three wayvalves can be particularly advantageous when the composition of the gasin a gas delivery tube, like for example a collinear fluid delivery tube112 or 114, is frequently changed between an inert fluid and achemically reactive fluid containing a reactive precursor molecule. Inone embodiment, the use of the modified collinear compound fluid flowdelivery assembly of FIGS. 20 and 21 in apparatus 20 is a method ofcontrolling the fluid flow to temporally intersperse single-fluid flowswith a fluid flow having two or more fluids. It is recognized that themass flow rates of fluids flowing through array 130 and outer sheath 80may differ for the flow velocities of all fluids to match at the fluidcontact point of apparatus 20 because gas velocity is dependent on thecross-sectional area of the exit orifice where the two fluids come intocontact. It is within the scope of the invention that the flow velocityof the gas in each of gas delivery tubes in the parallel gas deliverytube array 130 can be equal to the gas flow velocity of the gas flowingbetween outer sheath gas delivery tube 80 and array of parallel gasdelivery tubes 130. It is within the scope of the invention that theflow velocity of the gas in each of gas delivery tubes in the parallelgas delivery tube array 130 can be unequal to the gas flow velocity ofthe gas flowing between outer sheath gas delivery tube 80 and array ofparallel gas delivery tubes 130 thereby allowing gas dynamic focusing ofthe primary fluid. A compound collinear fluid flow is formed by thecombination of the fluid flows occurring at the exit of the array ofparallel gas delivery tubes 130. Each fluid flow in the compoundcollinear fluid flow is parallel to the same jet axis and the chemicalcomposition of gas in each gas delivery tube contributing to the totalfluid flow can be variable as a function of time. The formation of acollinear compound fluid flow is effective when flow velocities of allgasses in the gas delivery tubes are equal. It is preferred that theflow velocities of all fluid in the fluid delivery tubes are limited toregime of flow velocities exhibiting laminar flow characteristics as isfamiliar to those skilled in the art of fluid mechanics. In anotherembodiment, it can be advantageous in some embodiments to have the fluidvelocity of the secondary fluid larger than the fluid velocity of theprimary fluid and thus to have unequal fluid velocities at the exitlocation where the gases contact because this can be used to advantagefor hydrodynamic or gas dynamic focusing of the flow of one of thechemically reactive gases to further reduce the likelihood of fluiddelivery system contamination.

Further clarification of the disclosed inventive method of fluidiclevitation is furnished by the embodiment of an apparatus for fluidiclevitation of a moveable substrate with levitation stabilizing structureshown in FIG. 21. FIG. 21 is a cross-sectional view illustrating anotherembodiment of the present inventive method for practicing fluidiclevitation with chemically reactive fluids wherein the preferred fluidis a gaseous fluid. FIG. 21 shows a moveable substrate 10 with alevitation stabilizing structure 30 fabricated thereupon where thesurface of moveable substrate 10 with the levitation stabilizingstructure 30 opposes the gas emanating surface of stationary support 12with fluid collimating conduit 14. Fluid collimating conduit 14 is influid communication with a pressurized fluidic source emanating from anapparatus for production of compound fluid flows and jets 20 throughfluid outlet 19. Apparatus 20 is, in turn, in fluid communication withnon-reactive gas inlet 118 or reactive gas inlet 116 through valves 92,94, 96, and 98.

FIG. 21 illustrates the appropriate relative positions of the elementsmoveable substrate 10 with levitation stabilizing structure 30 relativeto the stationary support 12 through which fluid will flow and fluidcollimating conduit 14 for the use of levitation stabilizing structure30 to be effective as a method of positional stabilization duringfluidic levitation with an orthogonal jet emanating from fluidcollimating conduit 14. It has been found that the use of the levitationstabilizing structure as a method for improving the lateral stability ofa moveable substrate during pneumatic levitation only requires that thefluid jet from jet forming fluid collimating conduit 14 of stationarysupport 12 through which fluid will flow and impinge on the surface ofmoveable substrate 10 within the interior impingement area defined bythe surface bounded and enclosed by the walls of the levitationstabilizing structure 30 fabricated on the surface of moveable substrate10. It is preferred that the fluid jet from jet forming fluidcollimating conduit 14 of stationary fluid emitting support 12 impingeon the surface of moveable substrate 10 near the centroid of interiorimpingement area defined by the area enclosed by the interior walls ofthe levitation stabilizing structure 30 fabricated on the surface ofmoveable substrate 10. It is preferable that the centroid of theinterior impingement area enclosed by the interior walls of thelevitation stabilizing structure 30 fabricated on the surface ofmoveable substrate 10 be located within the impingement area enclosed bythe interior walls of the levitation stabilizing structure 30. The fluidcollimating conduit on the stationary fluid emitting support is analignment feature on the surface of the stationary fluid emanatingsupport and the centroid of the interior impingement area of thelevitation stabilizing structure is aligned with the alignment featurewherein the alignment feature is a fluid collimating conduit on thesurface of the stationary fluid emanating support. Thus, according tothe first three steps of the process sequence disclosed in FIG. 14 themethod for fluidic levitation includes the steps of:

1. providing a substrate with a levitation stabilizing structure on asurface of a substrate and positioning said substrate proximate to afluid emitting surface of a stationary fluid emanating support throughwhich fluid will flow in a conformal-wise manner with the levitationstabilizing structure overlaying the surface of the substrate and facingthe stationary fluid emanating surface;

2. initiating at least one collimated fluid flow from the stationaryfluid emanating support surface through which fluid will flow to producea collimated fluid jet; and,

3. controlling the collimated fluid flow emanating from the stationaryfluid emanating support to fluidically levitate the substrate andlevitation stabilizing structure proximate to the surface of thestationary fluid emanating support through which fluid will flow.

It has been observed experimentally that the alignment of the centroidof the interior impingement area of the levitation stabilizing structurewith at least one alignment feature on the surface of the stationaryfluid emanating support is not highly critical as the substrate with thelevitation stabilizing structure exhibits self-alignment during thelevitation process. The reasons for self-aligning behavior duringpneumatic levitation have been discussed previously. This is a distinctadvantage of using a levitation stabilizing structure during pneumaticlevitation.

FIG. 21 also shows an embodiment of an apparatus 20 for production ofcompound fluid flows and jets. The compound fluid flow forming apparatus20 is comprised of multiple elements including at least one modifiedcollinear compound fluid flow delivery assembly where the array 110 oftwo collinear fluid delivery tubes shown in FIG. 19 has been replacedwith an array 140 of collinear fluid delivery tubes comprised of threecollinear fluid delivery tubes. Apparatus 20 for production of compoundfluid flows is additionally comprised of means for controlling thetemperature, pressure, and flow of at least one fluid. The additionalmeans for controlling the temperature, pressure, and flow of at leastone fluid of compound fluid forming apparatus 20 of FIG. 21 are notshown. The modified collinear compound fluid flow delivery assembly inFIG. 21 is additionally comprised of collinear fluid delivery tube array140, outer sheath fluid delivery tube 80, and valves 92, 94, 96, and 98and provides a means for controlling the composition of the compoundfluid flow. The compound fluid forming apparatus 20 shown in FIG. 21 hasat least two inlets. Inlet 116 allows a first reactive fluid to flowinto apparatus 20 and inlet 118 allows a second non-reactive fluid toflow into apparatus 20. Apparatus 20 has a fluid outlet 19 in fluidcommunication with fluid collimating conduit 14. Fluid outlet 19 ofapparatus 20 may also serve as a means to alter the compound fluid flowusing hydrodynamic or gas dynamic focusing methods prior to formation ofa compound collinear jet emanating from fluid collimating conduit 14.The function of apparatus 20 is to combine at least 2 fluid flows, afirst fluid flow and a second fluid flow, to form a compositionallysegregated compound fluid flow exiting apparatus 20 through outlet 19and flowing though fluid collimating conduit 14 of the stationary fluidemitting support. In one embodiment the first fluid flow can be areactive fluid and the second fluid flow can be a non-reactive fluid andthe compound fluid flow is a collinear compound fluid flow. Unlike anyof the prior art utilizing fluid flows for fluidic levitation, apparatus20 is employed to produce a chemically reactive compound fluid flowexiting apparatus 20 at fluid outlet 19, said chemically reactivecompound fluid flow being a spatially non-uniform composition of mattercomprised of a chemically reactive fluid flow encased and surrounded bya chemically non-reactive fluid flow. A spatially non-uniformcomposition of matter is a composition of matter whose chemicalcomposition changes depending on the sampling location within thecomposition of matter volume. The said chemically reactive compoundfluid flow emanating from outlet 19 of apparatus 20 is injected throughfluid collimating conduit 14 to form a spatially non-uniform compoundjet that can be made non-reactive at the critical fluid contact regionsof the fluid delivery system employed for fluidic levitation by using achemically inert and chemically non-reactive fluid as the secondaryfluid that surrounds, contacts and encloses an inner primary fluid flowof chemically reactive fluid.

The modified compound collinear fluid flow delivery assembly shown aspart of apparatus 20 in FIG. 21 is now described in more detail.Collinear fluid delivery tubes of array 140 are in fluid communicationwith valves 94, 96, and 98 respectively. Valves 94, 96, and 98 are threeway controllable valves in fluid communication with reactive fluid inlet116 and chemically inert fluid inlet 118. Valve 92 is in fluidcommunication with inert fluid inlet 118 and valve 92 controls thesupply of chemically inert secondary fluid to the collinear compoundfluid exiting from apparatus 20 through fluid outlet 19. The switchablevalves 94, 96, and 98 determine the location of the chemically reactiveprimary fluid in the collinear compound fluid flow exiting outer sheathfluid delivery tube 80 and collinear fluid delivery tube array 140. Forexample, when switchable valve 94 allows fluid communication betweenreactive fluid inlet 116 and a collinear fluid delivery tube of array140, then the primary fluid flows through one of the collinear fluiddelivery tubes and the exiting compound fluid flow has a compositionalcross-section similar to that shown in FIG. 21c . Similarly in anotherembodiment, when switchable valve 96 allows fluid communication betweenreactive fluid inlet 16 and a collinear fluid delivery tube of array 140and the chemically reactive primary fluid flows through said collinearfluid delivery tube and the exiting compound fluid flow has acompositional cross-section again similar to that shown in FIG. 18c . Inboth configurations chemically inert secondary fluid flows in the volumebetween outer sheath fluid delivery tubes 80 and collinear fluiddelivery tube array 140. In another embodiment of apparatus 20 thedefault configuration of valves 92, 94, 96, and 98 allows chemicallyinert fluid to flow through all fluid delivery tubes in apparatus 20. Inanother embodiment of apparatus 20, the modified compound collinearfluid flow delivery assembly of FIG. 21 has outer sheath fluid deliverytube 80 extended beyond collinear fluid delivery tube array 140 andconnected directly to fluid collimating conduit 14 of the stationaryfluid emitting support by outlet 19 of apparatus 20. In an additionalembodiment, the internal diameter of outer sheath fluid delivery tube 80extended beyond collinear fluid delivery tubes array 140 is reduced in asmooth and monotonic fashion or the outlet 19 of apparatus 20 is reducedin a smooth and monotonic fashion to match the internal diameter offluid collimating conduit 14 thereby providing a way of hydrodynamicallyor gas dynamically focusing the collinear compound fluid flow prior toformation of the collinear compound jet emanating from fluid collimatingconduit 14 in the stationary fluid emitting support through which fluidwill flow. In apparatus 20, the fluid outlet 19 that is in fluidcommunication with fluid collimating conduit 14 can be convergent ordivergent, depending on whether the diameter of fluid collimatingconduit 14 is larger or smaller than the inner diameter of fluid outlet19. Regardless of the differences in diameter between fluid collimatingconduit 14 and outlet 19, it is desirable that the diameter of the twoelements 14 and 19 be equal at the point of fluid connection between thetwo elements 14 and 19. Thus, in one embodiment the cross-sectional areaof fluid outlet 19 is monotonically convergent between apparatus 20 andfluid collimating conduit 14 to enable matched interior cross-sectionalareas and cross-sectional shapes at the fluid communication junction ofapparatus 20 with fluid outlet 19 and to enable matched interiorcross-sectional areas and cross-sectional shapes at the fluidcommunication junction of fluid outlet 19 and fluid collimating conduit14.

The compound fluid forming apparatus 20 of FIG. 21 includes temperaturecontrol mechanisms, pressure control mechanisms, and flow controlmechanisms providing means for accurately controlling the temperature,pressure, and flow of the fluids that are employed for the purpose ofproducing a collimated compound fluid jet. A typical pressure controlmechanism for controlling pressure of gaseous and liquid fluids includeboth passively and actively controlled pressure regulators includingelectronically controlled pressure regulators and other types ofpressure regulator methods known in the art. A typical temperaturecontrol mechanism for controlling the temperature of a fluid includepassive and actively controlled heating and cooling units including heatexchangers, heating tapes and coils as well as cooling coils throughwhich the fluid passes, temperature controlled reservoirs, and otherdevices known to those skilled in the art of temperature control offluids. Temperature and pressure control loops employed to achievestable fluid temperatures and fluid pressures may incorporated the useautomated temperature and pressure control units. Typical means forcontrolling and measuring the flow of one or more gaseous fluids includethe use of orifices of known diameter with known pressure-flowrelationships, gas flow meters, flow controllers, control valves, andvariable control valves of all types including mass flow meters withvalves, mass flow controllers, rotameters with and without variablevalves, Coriolis flow meters coupled with flow controllers, turbine flowmeters, pitot based flow meters and other types of fluid flow metersfamiliar to those skilled in the art of process control of flowing fluidmedia where the fluid is a liquid or a gas.

The mechanisms for controlling fluid composition providing means forcontrolling the fluid composition are an important feature of theapparatus. For example, specific valve configurations can be employed inapparatus 20 of FIG. 21 to allow the apparatus 20 to produce compoundjets whose spatially non-uniform composition can be varied as a functionof time as the collinear compound fluid flows through fluid collimatingconduit 14. This is a distinct advantage because it allows the surfaceof moveable substrate 10 that opposes the stationary fluid emittingsupport to be exposed to a concentration of a reactive fluid for a knownamount of time. Exposure of a surface to a chemical species for a knownamount of time is also known as surface exposure or surface dosing andan apparatus that provides a means to dose a surface with a specificreactive fluid flow is extremely useful.

It is further recognized that the entire assembly represented by thecross-sectional view of FIG. 21 could be rotated by 180 around an axisnormal to the plane of FIG. 21 and the positional configuration willstill be functional. In other words, moveable substrate 10 can still besupported during levitation when the assembly shown in FIG. 21 isrotated and the fluid velocity vector of the orthogonal collimated fluidjet, compound or otherwise, is parallel to the direction ofgravitational pull. The use of a levitation stabilizing structure 30during fluidic levitation does not alter the function of a fluidiclevitation apparatus employing Bernoulli airflow with respect tophysical orientation or attitude of the apparatus, and in fact improvesthe robustness of fluidic levitation with respect to tilting of thegas-emanating stationary support regardless of the apparatus attitudeand orientation. Fluidic levitation can take place when the velocityvector of the orthogonal fluid jet is essentially parallel to thegravitational force vector or when the velocity vector of the orthogonalfluid jet is essentially anti-parallel to the gravitational forcevector. The presence of a levitation stabilizing structure 30 on themoveable substrate surface does not alter the relationships between thepneumatic forces that are generated by the fluid flow from theorthogonal jet that flows between the substrate surface and the fluidemitting support surface and the gravitational force vector that areinherently present in fluidic levitation processes employing Bernoulliairflow. This is a distinct advantage of the invention.

As was previously disclosed in FIG. 13, it is also recognized that thestationary support through which fluid will flow is not restricted to aplanar configuration as illustrated in FIG. 21. The features of thestationary support comprise the following: the stationary fluid emittingsupport contains at least one fluid collimating conduit in fluidcommunication with a manifold and a pressurized fluid source containingpressurized fluid, said fluid collimating conduit having across-sectional area less than or equal to ¼ of the surface area of theinterior impingement area of the levitation stabilizing structure; thesurface area of the stationary fluid emitting support is at least equalto the surface area of the interior impingement area on the moveablesubstrate; and the fluid flow between the stationary support and themoveable substrate is characterized by radial flow patterns that areessentially symmetric with respect to the centroid of the interiorimpingement area. It is preferred that said fluid collimating conduithave a cross-sectional area less than or equal to ¼ of the impingementarea enclosed by the walls of the levitation stabilizing structure.

Fluid mechanical models show that radial flow in the volume spacebetween two topographically conformal surfaces is achieved when anorthogonal jet emanating from the stationary support impinges on themoveable substrate and the cross-sectional area of the fluid collimatingconduit is less than or equal to ¼ of the opposing surface area of themoveable substrate and less than or equal to ¼ of the surface area ofthe stationary support that surrounds the fluid collimating conduit. Ifthe cross-sectional area of the fluid collimating conduit has a largercross-sectional surface area relative to the surface area of theopposing moveable substrate or the stationary support surface area, thenradial flow will not fully develop and the characteristic pressuredistributions (the low pressure radial flow expansion adjacent to thehigh pressure fluid jet impingement region) in the volume between theopposing moveable substrate surface and the stationary support surfacewill not fully develop leading to unpredictable fluidic levitation and,additionally, the levitation stabilizing structure will showunpredictable behavior with respect to stabilization of the moveablesubstrate lateral motion. The radial flow region in the volume between amoveable substrate and a stationary support is the volume region whereparallel surfaces are present as the fluid expand is a radial fashionfrom the orthogonal jet source. Topographically conformal surfaces arealso parallel surfaces in the sense that a normal extending from a pointon one surface is also normal to the opposing surface at the point ofintersection. When the moveable substrate is not topographicallyconformal to the stationary substrate radial flow diminishes, fluidiclevitation becomes unpredictable, and stabilization of the moveablesubstrate lateral motion by a levitation stabilizing structure on thesurface of the moveable substrate becomes unpredictable. Accordingly, inone embodiment, fully developed radial flow from an orthogonal jet inthe volume between the moveable substrate and the stationary support isachieved when the surface area of the stationary support is greater thanor equal to the surface area of the opposing moveable substrate so thatthe flow boundary for the radial flow region is the perimeter of themoveable substrate. For substrate processing of planar moveablesubstrates like silicon wafers or other planar substrates useful formicroelectronics applications, it is preferred that the surface area ofthe stationary support is greater than or equal to the surface area ofthe opposing moveable substrate. In another embodiment, fully developedradial flow from an orthogonal jet in the volume between the interiorimpingement area on the moveable substrate and the stationary support isachieved when the surface area of the stationary support is greater thanor equal to the surface area of the interior impingement area opposingmoveable substrate so that one flow boundary for the radial flow regionis the interior wall of the levitation stabilizing structure of themoveable substrate. Thus, for substrate processing of planar moveablesubstrates like silicon wafers or other planar substrate useful formicroelectronics applications, it is preferred that the surface area ofthe stationary support is greater than or equal to the surface area ofthe interior impingement area on the surface of the opposing moveablesubstrate.

The advantages of incorporating pneumatic levitation during substrateprocessing have been previously enumerated. The use of pneumaticlevitation is shown to be effective for film growth on the moveablesubstrate from the vapor phase such as is employed in vapor phaseepitaxy. The use of pneumatic levitation with levitation stabilizingstructures for atomic layer deposition is unknown but should beadvantaged due to the rapid gas exchange properties of radial flowduring pneumatic levitation with orthogonal jets. Without wishing to bebound by theory, it is thought that the rapid gas exchange leads toconditions where monolayer formation by surface adsorption processes onthe moveable substrate is limited by diffusion from the gaseous fluidthrough the fluid boundary layer at the moveable substrate surfacerather than by transport of reactants into and out of the reactionvolume surrounding the moveable substrate surface. During pneumaticlevitation of a moveable substrate using a single orthogonal jetemanating from a stationary support, the gas from the orthogonalimpinging jet expands radially into the surrounding volume. As the fluidexpands into cylindrical annuli of ever increasing radius, the volumeincrease of successive cylindrical annuli encountered as the fluid flowsradially outward is directly proportional to the distance from the jet.Thus, if a pulse or small quantity of material is injected into theorthogonal jet and produces a number density of ξ of molecules/unitvolume at the impingement location of jet, as these molecules flowradially outward and are diluted by additional flow the number densityof the molecules will vary as (ξ/r) where r is the radial distance fromthe impingement location of the orthogonal jet on the moveablesubstrate. In other words, the number density or concentration of themolecules in the volume between the stationary support and the moveablesubstrate will decrease in a manner inversely proportional to thedistance from the jet as the injected pulse flows radially outward. Atthe same time, both experimental measurements and theoreticalcalculations show that the velocity with which the molecules flowoutward falls off in a manner that is inversely proportional to r—whichmeans that the residence time of a molecule at a particular location isproportional to the distance from the jet. Thus, the product of theconcentration of molecules, (which is inversely proportional to r), andthe residence time, (which is proportional to r), is constant duringradial flow outward from the jet impingement location. The product ofconcentration or molecular number density and residence time is known asexposure, and is related to the amount of time that a surface is exposedto a given molecular flux. Dose is exposure multiplied by time. Theradial outward flow from the orthogonally impinging jet has the uniqueproperty that exposure of a surface to a vapor phase molecular speciesremains essentially constant as outward radial flow proceeds as long asthe consumption of the molecular species by secondary processes is smallin comparison to the initial molecular number density. This uniqueproperty of radial flow configurations is particularly advantageous forspecific deposition processes involving surface adsorption like, forexample, atomic layer deposition, or for any other process where uniformsurface exposure is important to achieve spatial uniformity of achemical reagent on a substrate surface. The velocities of the gaseousfluid phase as it undergoes outward radial expansion can be quite large.Gas velocities approaching the speed of sound are easily achievable andthese high gas velocities lead to very rapid gas exchange in the volumeregion defined by the gas emanating support surface and the opposingsurface of the moveable substrate. It is preferred that the gasvelocities during substrate processing remain subsonic in order tominimize effects of sonic shock waves that can interfere with masstransport. Depending on the pneumatic levitation height, gaseous volumeexchange as fast as 100 volume exchanges per second are possible. Theadvantages of rapid gas volume exchange have been previously disclosedin U.S. Pat. No. 5,370,709 with respect to vapor phase epitaxy processeswhere it is recognized that both particle contamination and chemicalcontamination by volatile impurities are minimized in processes whererapid gas exchange is present. Processes having rapid gas exchange canrun faster, leading to higher process throughput, especially if gasphase reactants or impurities must be removed by a purge step while theprocess is running. The rapid gas exchange that is inherent to pneumaticlevitation utilizing radial flow from a single orthogonal jet isparticularly well suited for processes like, for example, atomic layerdeposition or vapor priming, where gaseous reactants must be repeatedlyswept away from the substrate surface during the process sequence.

Contrary to the teachings of U.S. Pat. No. 5,370,709 concerning theadvantageous use of pneumatic levitation during substrate processinginvolving deposition processes, more recent art U.S. Pat. No. 6,289,842B1 by Tompa describes a plasma enhanced chemical vapor deposition systemthat is a vertical reactor with rotating disc substrates specificallyteaches that substrate levitation is not useful and is an impediment todeposition. U.S. Pat. No. 6,289,842 also specifically teaches the use ofphysical restraints to force the substrate to remain in a singleposition during deposition; however, U.S. Pat. No. 6,289,842 does notexamine pneumatic or hydraulic levitation as the method of levitationand does not teach or anticipate the use of pneumatic levitation duringdeposition or as a method of chemically reactive fluid delivery.Additionally, U.S. Pat. No. 6,289,842 does not teach the use of alevitation stabilizing structure to stabilize the moveable substrateposition during pneumatic levitation. The levitation method described inU.S. Pat. No. 6,289,842 involves levitation of a conducting substrate bya radiofrequency field thus, according to U.S. Pat. No. 6,289,842 thebeneficial and advantageous use of pneumatic levitation or hydrauliclevitation during substrate processing such as a chemical vapordeposition processing or an atomic layer deposition processing is notobvious.

U.S. Pat. No. 6,289,842 B1 teaches the use of a reactant gasdistribution unit having a chamber for providing a uniform flow ofcarrier gas and a gas distribution chamber that includes bafflingdesigned to preclude gas phase mixing of the reactants. Although acoaxial baffle configuration is disclosed in U.S. Pat. No. 6,289,842 B1,and the stated purpose of the coaxial baffle is for the separation ofreactive materials, the flow into and out of the coaxial baffles isthrough porous material of limited conductance and, as such, theconfiguration does not allow high gas flow or gas velocity that isrequired for fluidic levitation using Bernoulli levitation methods.Furthermore, the objective of the reactant gas distribution unit of U.S.Pat. No. 6,289,842 B1 is to produce a uniform gas flow over the surfaceof the rapidly rotating substrate. The porous materials and bafflingused in the reactant gas distribution unit taught in U.S. Pat. No.6,289,842 B1 are not compatible with the pressures and flow velocitiesrequired for the formation of high speed orthogonal jets employed forpneumatic levitation, especially at ambient pressures near atmosphericpressure. Compound fluid flows, coaxial compound fluid flows andcollinear compound fluid flows cannot be formed using the apparatusconfigurations taught in U.S. Pat. No. 6,289,842 B1. Therefore, the useof coaxial compound fluid flows or jets is not taught or anticipated byU.S. Pat. No. 6,289,842 B1. The use of compound jets in either acollinear or coaxial configuration for the segregation and delivery ofreactive gaseous precursors is not taught or anticipated by U.S. Pat.No. 6,289,842 B1. The use of compound jets in either a collinear orcoaxial configuration for the segregation and delivery of reactivegaseous precursors in a deposition process employing pneumaticlevitation of a moveable substrate with a levitation stabilizingstructure is not taught or anticipated by U.S. Pat. No. 6,289,842 B1.

In a separate publication Tompa et al. teach methods of simultaneouslyexposing the surface of a rotating substrate to a gas flow containingmore than one reactive precursor during metal-organic chemical vapordeposition processes. (G. S. Tompa, A. Colibaba-evulet, J. D. Cuchiaro,L. G. Provost, D. Hadnagy, T. Davenport, S. Sun, F. Chu, G. Fox, R. J.Doppelhammer, and G. Heubner (2001) “MOCVD Process Model for Depositionof Complex Oxide Ferroelectric Thin Films”, Integrated Ferroelectrics:An International Journal, 36:1-4, 135-152, DOI:10.1080/10584580108015536). Tompa discloses several embodiments ofcompositional variation of gases along streamlines that are usefulduring chemical vapor deposition processes. For the purposes of thisinvention, a streamline is the curve that is instantaneously tangent tovelocity vector of the flow at all times. Tompa teaches the use of gasflows in which the composition of the gas spatially varies along thestreamlines of the gas flow because the composition of the gas varies asa function of time—a method that is useful for deposition processes likeatomic layer deposition. Tompa further teaches that it is useful for thegas composition to vary both along stream lines, that is—parallel to thestream lines, as well as orthogonal to the stream lines, thatis—perpendicular to the stream lines of the flow. Tompa also teaches theuse of the resulting time varying gas flow embodiments for impingementon a substrate for the purposes of creating a thin film using thermaldecomposition of a reactive precursor. Prior art, especially U.S. Pat.No. 4,413,022, teaches that composition variation along gas stream linesis advantageous for the purposes of atomic layer deposition; U.S. Pat.No. 4,413,022 also teaches the use of compositional variationperpendicular the gas flow streamlines as being advantageous for atomiclayer deposition when combined with the use of a rotating substrate. Theuse of compound jets comprised of multiple collinear or coaxial jetsprovides a means to implement the compositional variation alongstreamline teachings of Tompa et al. and that of U.S. Pat. No. 4,413,022in an inventive manner that was not anticipated by the prior art.

FIGS. 15 through 21 show detailed configurations of embodiments ofapparatus 20 that can be incorporated into apparatus 150 to formcompound gaseous fluid flows. The compound gaseous fluid flow ofapparatus 150 is comprised of two or more gases including a first fluidand a second fluid wherein the first fluid is surrounded in at least onedimension by the second fluid and first and second fluid flows arecollinear. The compound fluid flow of two or more gases can include atleast a first, second and third fluids wherein the first fluid isseparated in at least one dimension by the second fluid. In oneembodiment, the apparatus 150 has a complex compound fluid flow whereinthe at least two fluids are separated in at least one dimension isachieved by sequential switching of valves in apparatus 20 incorporatedinto apparatus 150 thereby allowing the formation of complex fluid flowsof three or more fluids where the first fluid separated from the thirdfluid in at least one dimension by a second fluid. In one embodiment,the second fluid is inert. FIGS. 15, 16, and 17 illustrate portions ofan embodiment of apparatus 20 incorporated into process apparatus 150useful for forming the fluid flow in a collimated fluid flow comprisedof at least two fluid flows that are coaxial. FIGS. 18, 19, 20, and 21illustrate portions of an embodiment of apparatus 20 incorporated intoprocess apparatus 150 useful for forming the fluid flow in a collimatedfluid flow comprised of at least two fluid flows that are axiallycollinear. Pneumatic levitation of a substrate with a levitationstabilizing structure is a particularly useful method processing of asubstrate when no physical contact to the substrate during processing isdesired. FIG. 22 illustrates an embodiment of an apparatus for pneumaticlevitation of a moveable substrate with a levitation stabilizingstructure for the purpose of exposing the levitated substrate surface toa chemically or thermally reactive fluid during processing. Elements ofFIG. 22 are also common to chamber designs utilizing condensed fluidsduring the substrate processing that employ hydraulic levitation as amethod of non-contact substrate processing. Many processes can bemodified to take advantage of pneumatic levitation by incorporating theinvention of the levitation stabilizing structure on the moveablesubstrate. The apparatus of FIG. 22 provides a thin film depositionsystem for depositing a thin film on a moveable substrate usingatmospheric pressure atomic-layer deposition. The apparatus of FIG. 22for carrying out various processes on a substrate using pneumaticlevitation with a levitation stabilizing structure will now bediscussed.

FIG. 22 shows one embodiment of a pneumatically levitated moveablesubstrate processing apparatus 150. A container or chamber 152 isequipped with multiple feed throughs 1505. The chamber 152 can befabricated from any material that has suitable mechanical and chemicalproperties for use as a containment chamber for the fluids or chemicallyreactive fluids employed during the substrate processing and pneumaticlevitation of the substrate. Feed throughs 1505 provide communicationbetween the interior of chamber 152 and the exterior of chamber 152.Feed throughs 1505 are used to provide communication across the wall ofchamber 152 for fluids—said fluid being either liquid or gaseous oraerosol or dispersion. Feed through 1505 are used to providecommunication across the wall of chamber 152 for electrical powertransmission to elements of apparatus 150 located within chamber 152.Feed throughs 1505 are used to provide communication across the wall ofchamber 152 for electrical signals from sensors for control loops aswell as other types of electrical or mechanically generated signals thatare acquired to aid process operation. Feed throughs 1505 used toprovide electrical communication across the wall of chamber 152 forelectrical signals for the purpose of process control are sometimescalled instrumentation feed throughs 1505. Feed throughs 1505 may alsobe employed to provide communication of optical signals across the wallof chamber 152. Thus, feed throughs 1505 provide communication betweenthe interior of chamber 152 and the exterior of chamber 152 and areemployed to aid the execution of processes that are carried out on theinterior of the chamber 152.

The chamber 152 can be gas tight, in other words, the chamber can beconstructed so as to contain the gasses therein and preventcontamination of the internal gasses with substances located on theexterior of the chamber. In one embodiment, the atmosphere of chamber152 is at a pressure substantially equal to the air pressure outside thechamber. In a further embodiment, the atmosphere of chamber 152 has apressure greater than or equal to 1 psig. Typical gaseous contaminantsconsidered for exclusion are water, carbon dioxide, amines and ammonia,sulfur based volatile compounds, volatile hydrocarbons, and oxygen. Theprocess chamber 152 can include a means for monitoring the chemicalcomposition of the internal volume of the chamber (not shown). Suchmeans may include the use of spectroscopic methods such as massspectrometry and gas phase vibrational spectroscopy, gas phase opticalabsorption spectroscopies—including the use of cavity ringdownspectroscopy. A feed through 1505 (not shown) is employed to allow thespectroscopic measurement instrumentation or other process feedbackmeasurement instrumentation to communicate with the interior of chamber152. The process chamber can include transparent windows 1515 for thepurpose of visual process observation by human or machine observationmeans as well as for optional transmission of optical signals. Theprocess chamber optionally includes a way of measuring the pressure andtemperature inside the process chamber (not shown). The container orchamber 152 has a means for introducing and removing a sample, such as adoor with a fluid tight seal 1510 through with a sample can be passed,said door 1510 being equipped with a means to achieve gas tight sealingto prevent or minimize chamber contamination. The container or chamber152 also contains the stationary gas emitting support assembly 151 aswell as other additional elements that will now be further described.The door 1510 of chamber 152 can be made compatible with cluster tooldoor interlock geometries or may interface directly with a Front OpeningUnified Pod with a robotic automated material handling system forsequential processing of multiple substrates.

The process chamber 152 optionally includes a sample transport mechanismproviding means for transporting the moveable substrate sample throughdoor 1510 in and out of the container or chamber such as, for example, arobotic arm with a means to grasp the sample, such as an electrostaticchuck, a mechanical chuck, a Bernoulli wand, a Bernoulli chuck, a vacuumchuck, or a vacuum wand. An automatic material handling system can beinterfaced with the chamber 152 utilizing door 1510. Alternately, themoveable substrate sample may by handled manually and transported in andout through the door 1510 for the purposes of performing processes onthe moveable substrate sample.

The process apparatus 150 includes a stationary fluid emitting support12 through which fluid will flow with a surface area at least as largeas the surface area of the moveable substrate to be processed, saidstationary support through which fluid will flow containing at least onefluid collimating conduit 14 in fluid communication with a plenum ormanifold through fluid outlet 19, said plenum optionally contained inapparatus 20, that is in fluid communication with at least onepressurized source of gaseous fluid 1575 optionally through a feedthrough 1505. A moveable substrate 10 with a levitation stabilizingstructure 30 opposing the fluid emitting surface of the stationarysupport is also shown in FIG. 22 to illustrate an embodiment ofsubstrate positioning in apparatus 150.

The stationary support 12 through which fluid will flow can optionallybe equipped with temperature sensors, position and distance indicatingsensors to detect the presence of an opposing moveable substrate, a wayof heating the stationary support itself, and a temperature controlmechanism. The surface of gas-emanating stationary support assembly 12can be essentially planar for use with essentially planar substrates orthe surface of gas-emanating stationary support can be formed in such away as to approximately replicate the 3-dimensional negative image ofthe three dimensional topography one or more regions inherent to thesurface topography of the moveable substrate surface.

The process apparatus 150 includes a temperature control mechanismproviding a means for controlling the temperature of at least one fluid.The process apparatus 150 includes a temperature control mechanismproviding a means for controlling the temperature of one or more gaseousfluids contained in one or more plenums or manifolds, each plenum ormanifold being capable of fluid communication with the fluid collimatingconduit 14 of the stationary fluid emitting support 12. Temperature andpressure control units 1545 are used for controlling the temperature ofone or more gaseous fluids contained in one or more plenums or manifoldseach plenum or manifold being capable of fluid communication with thefluid collimating conduit 14 of the stationary fluid emitting support12. Typical means for controlling temperature of gaseous fluids includeboth passively and actively controlled gas heating assemblies, includingheating tapes and heat exchangers of any type familiar to those skilledin the art of temperature control. Typical means for controlling thetemperature of one or more gaseous fluids include temperature feedbackmechanisms controlling resistive heaters of all types, radiative heatersof all types, Hilsch vortex devices for production of hot and coldgases, inductive heating methods, the use of heat exchangers utilizingsecondary exchange fluids whose temperature is regulated by anytemperature control mechanism method familiar to those skilled in theart of heat exchangers and temperature control; methods of fluidtemperature control based on mixing of hot and cold fluids to regulategas temperature, and other temperature control methods familiar to thoseskilled in the art of process control of flowing fluid media. In oneembodiment, temperature and pressure control units 1545 are employed tocontrol the temperature of the inert gas flow from pressurized-gassource 1575, reactive precursor source #1 1565, and reactive precursorsource #2 1570 as well as controlling the flow of inert gas frompressurized—gas source 1575, the flow of reactive precursor #1 fromreactive precursor source #1 1565, and the flow of reactive precursor #2from reactive precursor source #2 1570 using flow controllers 1560. Inthe embodiment shown in FIG. 22, inert gas from pressurized-gas source1575 is a carrier gas for reactive precursor #1 from reactive precursorsource #1 1565 and inert gas from pressurized inert gas source 1575 is acarrier gas for reactive precursor #2 from reactive precursor source #21570.

The process apparatus 150 includes pressure control mechanism and a flowcontrol mechanism providing means for controlling the pressure 1545 andflow 1560 of one or more gaseous fluids contained in one or more plenumsor manifolds, each plenum or manifold being in fluid communication withthe fluid collimating conduit, nozzle, bore, or orifice of thestationary support. Typical means for controlling pressure of gaseousfluids include both passive and actively controlled pressure regulatorsand can be incorporated into the temperature and pressure control units1545. Typical means for controlling the flow 1560 of one or more gaseousfluids include gas flow meters and gas flow controllers of all typesincluding mass flow meters and mass flow controllers, rotameters withand without adjustment valves, turbine flow meters, pitot based flowmeters and other types of gas flow meters familiar to those skilled inthe art of process control of flowing gaseous media. In one embodimentshown in FIG. 22 the gaseous fluids employed during substrate processingare controlled by mass flow controllers equipped with mass flow meters1560 to allow precise control over the gas flow entering process chamber152 by stationary fluid emitting support 12 and optionally controllingthe mass flow of gases leaving the chamber by exhaust outlet 1530(exhaust flow control unit not shown).

The process apparatus 150 also includes a mechanism for forming compoundfluid flows providing a means for combining one or more fluids into alaminar flow and optionally includes a means for combining one or morefluids into a compound laminar flow possessing an outer sheath of inertchemically non-reactive gas that covers an inner core of chemicallyreactive gasses or gas mixtures. Apparatus 20 located inside chamber 152in fluid communication with fluid emitting stationary support 12 byfluid outlet 19 provides a way to combine one or more fluids into alaminar flow and optionally includes a structure for combining one ormore fluids into a compound laminar flow possessing an outer sheath ofinert chemically non-reactive gas that surrounds, is in contact with,and covers an inner core of chemically reactive gasses or gas mixtureswith optional hydrodynamic or gas dynamic focusing of the compoundlaminar flow. Compound jet forming apparatus 20 is in fluidcommunication with the fluids employed to provide either hydraulic orpneumatic levitation and provides a means for combining one or morefluids into a compound flow possessing an outer sheath of inertchemically non-reactive fluid that covers an inner core of chemicallyreactive fluids or fluid mixtures. A preferred fluid type is a gas or agas mixture. In one embodiment, the compound flow may havecharacteristics of a coaxial flow where the inner region of gas isaxially symmetric with the outer sheath of inert gas direction of flowas would be produced by an embodiment of apparatus 20 similar to thatillustrated in FIGS. 16 and 17. In another embodiment, the compound flowmay have the characteristics of a collinear flow where the inner regionof reactive is flowing in the same direction as the outer sheath ofinert gas but is not axially symmetric with respect to the outer inertgas sheath direction of flow as would be produced by an embodiment ofapparatus 20 similar to that illustrated in FIG. 21. A compound flow isconsidered axially symmetric if the chemical composition of the gases,examined in the direction perpendicular to the flow direction, appearsunchanged when rotated about an axis defined by the flow direction.Similarly, a compound flow is considered collinear if the chemicalcomposition of the gases, examined in the direction perpendicular to theflow direction, appears to change when rotated about an axis defined bythe flow direction. Compound flows can be formed by employing, forexample, an embodiment of apparatus 20 designed according to theprinciples illustrated in FIG. 17 and FIG. 21 to combine fluid flows forthe purpose of producing collinear or coaxial compound fluid flows aspreviously described. The compound fluid flows can be used to producecolumnar compound fluid jets emanating from stationary fluid emittingsupport assembly 12 through which fluid will flow by injection of thefluid flow through fluid outlet 19 (not shown) with optionalhydrodynamic focusing of the compound fluid flow to fluid collimatingconduit 14 through which one or more fluids flow and the columnarcompound fluid jets emanating from the surface of stationary supportassembly 12 can be coaxial or collinear.

In one embodiment the compound jet formation apparatus 20 is in fluidcommunication with a plurality of fluids through feed through 1505 thatis in fluid communication with a fluidic network which is shown in FIG.22 to reside on the exterior of the chamber 152. FIG. 22 shows thecompound jet formation apparatus 20 in fluid communication with reactiveprecursor source #1, 1565, pressurized gas source, 1575, reactiveprecursor source #2, 1570, each fluid source controlled independently bymass flow controllers 1560 that are controlled by a valve sequencecontrol unit 1555. The valve sequence control unit 1555 determines howmuch flow each mass controller valve 1560 allows to flow into compoundjet formation apparatus 20, thereby providing a way of adjusting thecomposition of the compound jet exiting the stationary fluid emittingsupport assembly 12 through which fluid will flow through fluidcollimating conduit 14. The valve sequence control unit 1555 provides away of providing temporal as well as spatial variation in the gascomposition of the compound jet formed by the compound jet formationapparatus 20. The temporal variation of the composition of a compoundjet is useful for vapor phase deposition processes such as chemicalvapor deposition and atomic layer deposition according to the processstep diagram of FIG. 14. Other configurations of the fluidic network andcompound jet formation apparatus 20 are, of course, possible within thespirit and scope of the apparatus shown in FIG. 22.

Apparatus 20 provides a mechanism for providing a single-gas flow of aninert fluid or inert gaseous fluid to process apparatus 150. Apparatus20 provides a mechanism for controlling the fluid flow and chemicalcomposition of the fluid flow to alternately provide an inertsingle-fluid flow with a reactive fluid flow having an inert fluid and areactive fluid to the stationary fluid emitting support in processapparatus 150. Apparatus 20 provides a mechanism for controlling thefluid flow to alternately provide a first reactive fluid flow having aninert fluid and a first reactive fluid and a second reactive fluid flowhaving an inert fluid and a second reactive fluid different from thefirst reactive fluid to the stationary fluid emitting support in processapparatus 150. Apparatus 20 and stationary fluid emitting support 12provide a mechanism for forming the fluid flow of two or more fluidsinto a columnar compound fluid jet that is coaxial or collinear.Apparatus 20 provides a mechanism for providing a fluid flow includingat least a first reactive fluid, a second inert fluid, and a thirdreactive fluid wherein the first and second reactive fluids arespatially separated by the second inert fluid in at least one dimension.Apparatus 20 provides a mechanism for providing two or more fluids atthe same time from a pressurized—fluid source through the stationarysupport into the gap so that the fluid flow impinges on at least aportion of the substrate and exposes the substrate portion to the fluidto deposit a thin film on the substrate.

It is recognized that process apparatus 150 can be operated over a widevariety of internal chamber pressures. The internal operating pressureof process apparatus 150 can be above atmospheric pressure with aninternal chamber pressure of at least 1 psig. The internal operatingpressure of process apparatus 150 can be below atmospheric pressure. Aspreviously discussed, the ambient environment around the moveablesubstrate during levitation is a factor in the levitation process andpneumatic levitation of a moveable substrate can be accomplished in bothelevated and reduced pressure environments.

The process apparatus 150 includes a mechanism for exhausting fluidsfrom process chamber 152 that provides a means for exhausting thegaseous fluid emanating from the surface from the stationary fluidemitting support 12. The exhausting of the gaseous fluid may utilize anynumber of means, such as pumping through exhaust port 1530 with amatched process flow using a throttle valve (not shown) at pre-setchamber pressure; venting the chamber gas through exhaust port 1530 at apre-set chamber pressure using a pre-set process flow controlled by athrottle valve and a structure that measures the exhaust flow throughexhaust port 1530; or more simplistically, allowing the chamber toexhaust through an orifice or an array of multiple orifices of knownconductance connected to a plenum or manifold incorporated into exhaustport 1530 as a method of controlling exhaust flow. It is advantageous toa have supplemental laminar flow supplied to chamber 152 as is customaryin the design of chemical reactors utilizing continuous fluid flow. Asupplemental gas flow is provided by gas distribution assembly 1520 influid communication with a mass flow controller 1560. The gasdistribution assembly 1520 of process apparatus 150 can be a showerheadcomprised of a plurality of nozzles, orifices, bores, or gas deliverytubes in fluid communication with a pressurized-gas source to achievelaminar flow of gas from the gas distribution assembly 1520 to theexhaust outlet 1530. Mass flow controller 1560 supplying pressurized-gasto the gas distribution assembly 1520 is in fluid communication with apressurized source of inert gas 1575 whose temperature and pressure iscontrolled by temperature and pressure control until 1545. Furthermore,it is advantageous for the purpose of particle control to allow theexhaust flow from stationary fluid emitting support 12 to mix with andbe entrained by an additional laminar flow of gas moving along theinterior walls of the container or chamber to minimize chemical andparticle contamination of the interior of the chamber—a method that iswell known to those skilled in the art of process chamber design forprocess equipment. The fluidic flow in the chamber 152 exits apparatus150 through exhaust port 1530 where it is directed to a suitablescrubbing unit for removal of any potentially hazardous exhaustmaterials.

Part of the exhaust flow in chamber 152 can be supplied by a flowcontrol structure 1580 located proximate to the stationary fluidemitting support. In one embodiment shown in FIG. 25a flow controlstructure 1580 in chamber 152 is located proximate to the fluid emittingstationary support 12 and is supplied by a flow control structurecomprised of an annular tilted fluid emitting slot or ring nozzlesurrounding the stationary support and directing an exhaust flow towardsthe chamber exhaust. In one embodiment the annular tilted fluid emittingslot assembly is similar to an air amplifier, also called herein a gasamplifier, operating with an inert gas wherein the inert gas is nitrogenor argon and the exhaust of the amplifier is directed towards thechamber exhaust. In another embodiment shown in FIG. 26 the flow controlstructure 1580 is comprised of at least one gas amplifier, each gasamplifier operating with inert gas, wherein the intake surface of eachgas amplifier is coplanar with the fluid emitting surface of thestationary support structure 12 and all exhaust fluid flows through theflow control structure. In a further embodiment, the flow controlstructure of FIG. 26 is in fluid contact with the exhaust outlet throughone or more lengths of gas-tight tubing. The disclosed embodiments areparticularly advantageous for operation at atmospheric pressure andabove and under conditions where the mean free path of the gas is atleast 100 times smaller than the largest physical dimension of the flowcontrol structure because a flow control structure comprised of gas flowamplifiers is efficient in managing aerosol and gas-based contaminationby effective gas and aerosol entrainment in the amplified exhaust flowexiting the flow control structure.

Referring to FIG. 25, the principle by which the pneumatic flow controlstructure operates is as follows: high pressure gas is injected throughthe annular nozzle 1582 at high velocity and the high velocity gas flowadheres to the internal profile 1584 of flow control structure 1580 bythe Coanda effect and the change in velocity of the injected highpressure gas results in reduced pressure proximate to the annularnozzle. The reduced pressure proximate to the annular nozzle induces ahigh volume flow of surrounding gas into the high velocity flow at theinternal profile of the flow control structure 1580 resulting in a highvolume, high velocity flow directed at the exhaust outlet 1530.

It can also be desirable in some applications to heat the walls of theprocess chamber 152 during processing as it is known in the art ofdeposition that thermal energy applied to the walls of a process chambersuch as process chamber 152 is advantageous for process control andprocess cleanliness. Thus, chamber 152 can optionally have heated walls,said heated walls being heated by means familiar to those in thoseskilled in the art of chamber design including temperature controlledheating tapes and pads; heat exchanging tubing mounted on the exteriorof chamber 152 through with temperature controlled fluids are passed;radiant heating of the chamber walls employing radiation heating sourceslike, for example, infrared radiation heating sources; and other knownmethods of controlling the temperature of process chamber walls.

The process apparatus 150 can also include a mechanism for determiningmoveable substrate position providing a means (not shown) for providingfeedback indicating the state of the moveable substrate with respect topneumatic levitation of the moveable substrate to determine, forexample, whether pneumatic levitation of the moveable substrate has beenachieved. Means for verifying pneumatic levitation include opticalimaging methods with video cameras that are computer analyzed;reflective methods utilizing displacement of an optical beam from apredefined path to determine whether the moveable substrate islevitating; detection of moveable substrate height variation usingoptical methods such as low coherence interferometry or other methodssuch as the use of capacitance sensors or an array of position anddistance sensitive sensors of any type familiar to those skilled in theart of position and distance sensing. Methods for sensing moveablesubstrate position are disclosed in, for example, U.S. Pat. No.8,057,602 B2.

The process apparatus 150 can also include temperature control mechanismproviding a means for heating the moveable substrate 10 and controllingthe temperature of the moveable substrate as well as an optional meansfor heating the gas emanating stationary support and controlling thetemperature of the gas emanating stationary support (not shown). In oneembodiment, the moveable substrate 10 is heated by heater 1535 locatedinside process chamber 152. Moveable substrate and stationary supporttemperature control unit 1550 is part of a temperature control mechanismof chamber 150 and provides a means for controlling the heating of themoveable substrate utilizing moveable substrate heater 1535 as well asan optional means for controlling the heating the gas emanatingstationary support. In one embodiment the stationary support temperaturecontrol unit to moveable substrate heater 1535 is in electricalcommunication with heater 1535 and optionally heaters incorporated intothe stationary support assembly 12 (not shown) by feed throughs 1505.

The moveable substrate and stationary support temperature control unitcan supply electrical energy or other forms of energy, such as radiofrequency or microwave energy, that are used to control the temperatureof the moveable substrate and the stationary support assembly. In oneembodiment of the temperature control mechanism, the moveable substrateand stationary support temperature control unit supplies radiofrequencyenergy to both the moveable substrate and the stationary supportassembly. In another embodiment, the energy supplied by the moveablesubstrate stationary support temperature control unit is converted toinfrared radiant energy by moveable substrate heater 1535. In theembodiment shown in FIG. 25, substrate heater 1535 is shown enclosedwithin process chamber 152; however, alternatively, substrate heater1535 of process apparatus 150 can be located outside of process chamber152 and the energy for heater transmitted through the walls of processchamber 152 for the purpose of heating substrate 10 and optionallystationary fluid emitting support 12. Infrared energy and radiofrequencyenergy are examples of energy for heating moveable substrate 10 that aretransmissible through the walls of chamber 152 when process chamber 152is constructed out of appropriate materials. In another embodiment ofprocess chamber 150, heating of both the moveable substrate and thestationary support and the temperature control mechanism for heating ofboth the moveable substrate and the stationary support can be achievedby any method familiar to those skilled in the art of heating and heattransfer including, radiative heating, resistive heating, inductiveheating, microwave heating, control of the temperature of the stationarysupport by the use of heat transfer fluids, control of the temperatureof the moveable substrate by the use of heated gases emanating from thestationary support.

In one embodiment, as taught in U.S. Pat. No. 5,370,709 by Kobayashi, atransparent window that is used to allow transmission of the infraredradiant energy for the purpose of heating the substrate and the exhaustgas flow can be designed around the transmission area for the infraredradiation from a radiant light source that is used to heat the substrateand the method of generating a laminar exhaust flow in chamber 152 canbe substantially different from what is shown in FIG. 22. In oneembodiment not taught or disclosed in U.S. Pat. No. 5,370,709, themajority of the volume of the supplemental laminar exhaust flow can besupplied by a polygonal shaped annular duct where the emitted flow fromsaid polygonal shaped annular duct is directed essentially at thelocations near the perimeter of the levitating substrate where theprocess effluent is primarily emitted.

In an embodiment of process chamber 150 shown in FIG. 22a temperaturecontrol mechanism comprised of a temperature measurement mechanism 1540and the use of a temperature feedback loop supplied by temperaturecontrol unit 1550 is advantageous for enabling reproducible processeswith fluidic levitation, particularly with pneumatic levitation. In oneembodiment of the temperature control mechanism, temperature sensing ofthe moveable substrate is provided by temperature measurement sensor1540 and is preferably a non-contact temperature measurement method inorder to preserve the advantage of non-contact processing withunrestricted natural motion of the substrate with levitation stabilizingstructure during fluidic levitation. In another embodiment of thetemperature control mechanism, temperature sensing of the stationaryfluid emitting support 12 is provided by temperature measurement sensor(not shown) that is attached to the stationary support assembly.Temperature sensing can be achieved by any means familiar to thoseskilled in the art of temperature measurements including the use ofthermocouple, resistance temperature detectors (RTDs), thermistors, andother types of calibrated resistors and electrical components such astemperature sensitive diodes whose electrical properties changes as afunction of temperature, as well as the sensing of temperature with ameasurement of infrared radiation emitted by the object of interest.Other methods for temperature sensing include the use of opticallyexcited fluorescence signals, calibrated dilatometric methods as well assensing of secondary process variables such as gas temperature throughany known means such as the use of a thermocouple as well as temperaturemeasurements based on other physical properties such fluid viscosity.The determination of the temperature of the moveable substrate and thestationary support assembly is accomplished by the temperature controlunit 1550 that is equipped with electrical circuits whose function isthe conversion of the output signal received from said temperaturesensor into a calibrated temperature measurement.

Process apparatus 150 employing an orthogonal fluid jet for fluidiclevitation with radial flow provides a method for thermally isolatingthe moveable substrate and its surfaces from physical contact with anythermal sinks, thereby enabling effective temperature control for bothheating and cooling—especially during the use of optional processingsteps involving high photon flux radiative exposures such as optionallyradiative curing with either IR or UV radiation. The use of processingsteps involving the use of radiation of all types for the purposes ofsupplemental processing of moveable substrates with levitationstabilizing structures during pneumatic levitation is specificallycontemplated and considered inclusive in process apparatus 150 and suchradiation sources may include ionizing radiation sources such as x-rays,alpha rays, beta rays, electron beams, gamma rays, and the like as wellas lower photon energy radiation types such as ultraviolet radiation,visible photon radiation that is photochemically active, and infraredradiation. The use of microwave radiation during processing isspecifically contemplated as applied to the pneumatic levitation of amoveable substrate with a levitation stabilizing structure. The use ofterahertz radiation during processing is specifically contemplated asapplied to the pneumatic levitation of a moveable substrate with alevitation stabilizing structure. The rapid radial flow in the volumebetween the moveable support surface with its levitation stabilizationstructure and the gas-emanating stationary support enables excellentcleanliness and low contamination during deposition processes executedat elevated temperatures as well as the capability to induce rapidcooling once heating is discontinued. The effluent fluid from theprocess is optionally managed by the use of a supplemental laminar flowof inert gas around the moveable substrate and stationary support forthe purpose of removing the gaseous process effluent from the regionproximate to the moveable substrate and the stationary support assemblyfor disposal. U.S. Pat. No. 5,370,709 has previously disclosed thermalannealing processes and deposition processes using reactive precursorsby employing pneumatic levitation with a single orifice (or single fluidcollimating conduit) but the apparatus disclosed therein required theuse of physical stops to prevent the substrate from sliding off the“suction plate”. Deposition processes employing pneumatic levitationwithout the use of substrate motion restraining structures such asphysical stops on the stationary support plate are not contemplated inU.S. Pat. No. 5,370,709. The use of supplemental exposure of themoveable substrate to ionizing radiation as part of substrate processingduring fluidic levitation is not contemplated in U.S. Pat. No.5,370,709. The use of supplemental exposure of the moveable substrate tophotochemically active radiation as part of substrate processing duringfluidic levitation is not contemplated in U.S. Pat. No. 5,370,709.

Thus, the apparatus 150 shown in FIG. 22 achieves one or more of thefollowing objectives:

fluidically levitating a moveable substrate with a levitationstabilizing structure over a stationary support assembly 12 throughwhich fluid will flow using an orthogonal compound jet originating atfluid collimating conduit 14;

forming a compound jet of variable chemical composition using a compoundjet formation assembly 20;

controlling the flow of the compound jet formed using the compound jetformation assembly 20;

controlling the chemical composition of the compound jet formed usingthe compound jet formation assembly 20;

controlling the temperature of the levitating moveable substrate 10 witha levitation stabilizing structure 30;

optionally controlling the temperature of the process chamber 152;

controlling the temperature of all fluids in the process chamber 152;

controlling the temperature of the stationary support assembly 12;

forming an orthogonal compound jet for the purposes of fluidiclevitation of a moveable substrate with a levitation stabilizingstructure of apparatus 20 and fluid collimating conduit 14;

exposing a pneumatically levitated substrate to a chemically reactivefluid during pneumatic levitation;

inserting and positioning a moveable substrate inside an apparatus overa stationary support assembly at a location suitable for fluidiclevitation;

removing a moveable substrate from an apparatus;

controlling the gas composition of a compound jet used for fluidiclevitation and providing a means for varying the chemical composition ofa compound jet as a function of time, said compound jet being eithercoaxial or collinear; or

controlling the exhaust flow from an apparatus used for fluidiclevitation in a controlled fashion for the purposes of proper effluentmanagement and disposal.

Other embodiments of the inventive concepts herein disclosed arepossible and fall with the contemplated spirit and scope of theinventive method and apparatus.

The differences between the present atmospheric pressure depositionmethod and two other methods of atomic layer deposition disclosed in theart can be further understood by considering the mean free path of thegas molecules of the fluid during substrate processing, regardless ofwhether the substrate is fluidically levitated. The mean free path ofthe inert gas Argon at a given temperature and pressure can becalculated by the formula

$l = \frac{k_{b}T}{2\pi\; d_{o}^{2}P}$where k_(b) is Boltzmann's constant, T is the temperature in Kelvin, Pis the pressure in Pascals, and d_(o) is the molecular diameter of themonatomic Argon gas molecule.

Suntola et al (U.S. Pat. No. 4,413,022) disclosed a method of atomiclayer deposition that is commonly employed for substrate processing andSuntola's method requires well controlled gaseous mass transport with alarge mean free path that is characteristic of laminar viscous flow of alow pressure gaseous fluid as is found at sub-atmospheric Argonpressures between 50 Pa and 10,000 Pa where the mean free path of Argonmolecules in the gaseous fluid is constant and has values between 200microns and 1 microns, respectively. In contrast to the method ofSuntola, the method of spatial atomic deposition disclosed by Levy (U.S.Pat. No. 7,413,982) requires a laminar viscous flow of gaseous fluidwith a gas pressure sufficient high to provide gas bearing behavior whenthe pneumatic fluid is trapped between two surfaces and surrounded byatmospheric pressure. The pneumatic pressure employed in Levy's methodis typically above atmospheric pressure, (between 100,000 Pa and 300,000Pa). At the gas pressures required for gas bearing operation in Levy'smethod, the free path of Argon molecules in the gaseous fluid isconstant with a maximum value of around 0.1 microns and a typical meanfree path of the molecules in the gas phase that is smaller than 0.1microns at the higher gas pressures required for gas bearing operation.In both the method of Suntola and the method of Levy the operatingpressure in the volume region where deposition takes place isstatic—that is, the pressure in the volume region where the depositiontakes place is essentially constant and unchanging therefore the meanfree path of the molecules in the gas phase is constant duringprocessing. The process fluid pressure is constant in the method ofSuntola because of the process requirement that laminar flow be constantthroughout all process steps for predictable mass transport. Similarly,the method of Levy also requires constant positive pressure above thedeposition regions for constant mass transport during the process andalso for proper operation of the gas bearing transport mechanism that isutilized by Levy's method to achieve spatially separated sequentialreagent exposure on the substrate surface during the deposition processcycles where the apparatus and substrate move relative to each other. Inboth these methods, the mean free path of the molecules in the gaseousfluid is constant in the volume of the deposition apparatus wheredeposition occurs during substrate processing.

In contrast to the methods of Suntola and Levy, the method disclosed inthe present invention employs outward radial flow from a central gasinlet (sometimes called Bernoulli flow) to enable a spatially varyingpressure distribution in the volume where the deposition process takesplace and proximate to the surface of the moveable substrate upon whichdeposition occurs. As a result of the spatially varying pressuredistribution, the mean free path of the gaseous fluid is not constant inthe volume where the deposition takes place and fluid mechanic modelscombined with mean free path calculations show that the mean free pathof gaseous Argon molecules in the deposition volume of the presentinvention can vary by as much as a factor of 5 (between 0.06 microns and0.33 microns) or more when the inventive process is operated using amoveable substrate comprised of a 150 mm silicon wafer with a 128 mm IDlevitation stabilizing structure extending 240 microns from the moveablesubstrate surface and employing a fluid pressure at the stationary fluidemitting support of around 160,000 Pa at 101,000 Pa ambient pressure.The minimum mean free path of the gaseous Argon molecules in the presentinvention is determined by the pressure of the gaseous fluid jetrequired to achieve the desired height of pneumatic levitation of themoveable substrate. The pressure of the gaseous fluid jet required toachieve pneumatic levitation of the substrate is, in turn, influenced byseveral factors, one of the most important factors being the substrateweight and size. Another factor limiting the pressure of the gaseousfluid jet required to achieve pneumatic levitation of the substrate inthe present inventive method is the preferred practice of the inventionwherein the gaseous fluid velocity remain sub-sonic—that is below thespeed of sound in the fluid—in order to avoid the formation of turbulentflow in the volume between the moveable substrate and the stationaryfluid emitting support. Pneumatic levitation of a moveable substratewith a levitation stabilizing structure occurs in the present inventionwhen the sum of all the pneumatic forces acting on the moveablesubstrate opposes and exceeds the force of gravity on the moveablesubstrate. There is a range of pressures wherein the present inventivemethod operates because the sum of all the pneumatic forces acting onthe substrate to oppose the gravitational force on the moveablesubstrate is comprised of multiple pneumatic forces including theambient pneumatic pressure as well as the pneumatic forces resultingfrom the fluid emanating from the stationary fluid emanating support.The ambient pneumatic pressure is determined by the immediateenvironment around the moveable substrate and the stationary fluidemitting support. In an embodiment, the moveable substrate and thestationary fluid emitting support can be in a process chamber as shownin apparatus 150 of FIG. 22, and the ambient pressure that is determinedby the pressure in the process chamber can vary over a wide pressurerange from 10 pascals to megapascals (10⁶ pascals).

Examples of applications of levitation stabilizing structures tomoveable substrate processing are discussed below.

In one embodiment a moveable substrate may utilize a levitationstabilizing structure fabricated thereupon for the purpose of achievingpneumatic levitation to minimize physical contact with moveablesubstrate during transport as well during storage, thereby providing amethod for employing pneumatic levitation to minimize physical contactto a moveable substrate during transport and storage. A linear array oforthogonal jets that is suitably spaced relative to the dimensions ofthe moveable substrate with the levitation stabilizing structure willallow the substrate to be physically moved over the length of theorthogonal jet array with no physical contact to the substrate. Theinitial horizontal motion can be initiated by any number of means,including moveable substrate displacement initiated using a pneumaticforce produced by a tilted gas jet impinging on any surface of themoveable substrate similar to that described by Yokajty in U.S. Pat. No.5,470,420.

A levitation stabilizing structure fabricated on a moveable substratecan be employed to provide a method of stable pneumatic levitation ofthe moveable substrate during various processes used to modify thesubstrate properties. Examples of processes used to modify the substrateproperties include surface cleaning, surface modification, thermalannealing, laser scribing, aerosol deposition, surface etching, chemicalvapor deposition, atomic layer deposition, self-assembled monolayerdeposition, and other processes employed to modify the properties of themoveable substrate are given below.

The scope of application of the fluid levitation stabilization throughthe use of levitation stabilizing structure is, of course, not limitedto just the disclosed process embodiments and it is recognized thatother processes used to modify a moveable substrate can benefit when alevitation stabilizing structure in employed to achieve stable fluidlevitation during process execution. Such embodiments may includeprocesses in which the fluid is non-compressible, such as anon-compressible or incompressible liquid, rather than a gas. Theapplication of the levitation stabilizing structure to various processeswill now be described further. In the exemplary process embodimentsdisclosed below, the process steps disclosed in FIG. 14 can be followedwith respect to the use of fluidic levitation during processing of thesubstrate with levitation stabilizing structure.

Exemplary Process Embodiment 1

A moveable substrate with a levitation stabilizing structure employed ina cleaning process with pneumatic levitation.

In one method embodiment a moveable substrate with levitationstabilizing structure is placed in a chamber upon a transparent UVtransmitting gas-emanating stationary support. The moveable substrate isplaced so that the levitation stabilizing structure is facing oropposing the gas-emanating stationary support. The stationary UVtransmitting gas emanating support is made of, for example—vitreoussilicon oxide, and equipped with an ultraviolet radiation source such asa high intensity UV emitting plasma lamp positioned to radiate UVradiation through the UV transmitting gas-emanating stationary supportonto the opposing surface of the moveable substrate. Alternately, thegas-emanating stationary support can be opaque and the moveable samplecan be irradiated with UV radiation on the side which does not face thegas-emanating stationary support. In yet another embodiment, both sidesof the moveable substrate can be irradiated at once using a plurality ofirradiating sources. The stationary support contains a fluid collimatingconduit in fluid communication with an oxygen bearing gas, such as pureoxygen or an ozone bearing gas such as the effluent from a dielectricbarrier discharge ozone generator. UV-ozone cleaning can be achievedduring levitation of the moveable substrate when the substrate surfacefacing the UV emitting radiation source is irradiated with ultravioletradiation having at least emissions between 180 nm and 300 nm whenemploying a cleaning fluid, for example, an oxygen containing gas orozone containing gas as the gaseous cleaning fluid emanating from thestationary support surface for pneumatic levitation. In this example thechemical composition of the material layer employed to fabricate thelevitation stabilizing structure should be considered to ensure that theLSS remains intact during UV-ozone cleaning due to the corrosive natureof UV-ozone exposure to certain types of material compositions. Anadvantage to the method is the rapid gas exchange ensuring rapid processeffluent removal during cleaning. In one embodiment, the cleaning fluidis surrounded by the inert gas and serves to clean the moveablesubstrate. In another embodiment, the cleaning fluid is not surroundedby the inert gas and serves to clean both the moveable substrate and theinterior surfaces of apparatus 20 and fluid outlet 19.

Exemplary Process Embodiment 2

A moveable substrate with a levitation stabilizing structure employed ina surface modification process with pneumatic levitation.

In another method embodiment a moveable substrate with levitationstabilizing structure where the substrate has a surface of hydratedsilicon oxide with exposed surface hydroxyl groups is placed in processapparatus 150 upon a gas-emanating stationary support. The moveablesubstrate with levitation stabilizing structure and exposed surfacehydroxyl groups is placed so that the levitation stabilizing structureis facing or opposing the gas-emanating stationary support and themoveable support is pneumatically levitated by a gaseous fluid. Thestationary support contains a fluid collimating conduit in fluidcommunication with a gas containing a reactive vapor phase precursorthat is generated by apparatus 20. The gaseous fluid composition ischosen to contain a reactive vapor phase precursor that reacts with themoveable substrate surface and exposed surface hydroxyl groups in such away as to uniformly expose the moveable substrate surface to themolecular vapor of the reactive precursor with the intent of forming amolecular layer or monolayer of a chemical composition similar to thereactive precursor on the surface of the moveable substrate. Pneumaticlevitation is used as method for exposing the moveable substrate surfaceto a molecular flux of the reactive precursor. The gas containing areactive vapor phase precursor may optionally be a compound fluid flow,said fluid flow being either a coaxial compound fluid flow or acollinear compound fluid flow. The conditions of radial flow duringpneumatic levitation with an orthogonal jet are favorable for theformation of uniform molecular layers because, as previously discussed,the exposure of the moveable substrate surface (which equals themolecular flux to the surface multiplied by the amount of time thesurface is in contact with the molecular flux) is uniform over theentire surface area that is exposed to radial flow. In one embodiment,the reactive vapor phase precursor can be a member of the class ofcompounds known as fluoroalkyl-trichlorosilanes which are known to behighly reactive with hydrated silicon oxide surfaces and are used forthe formation of low surface energy self-assembled monolayers. Exposureof the hydrated silicon oxide surface to vapor phasefluoroalkyl-trichlorosilanes will result in liberation of HCL gas andthe formation of an fluoroalkyl polysiloxane monolayer that ischemically bonded to the silicon oxide surface where the organicfunctional groups are oriented so that they face outwards from thesubstrate surface, thereby imparting substantially different,Teflon-like chemical properties to the silicon oxide surface. Optionallythe moveable substrate with levitation stabilizing structure can beheated during exposure of the substrate surface to thefluoroalkyl-trichlorosilane vapor to improve the surface mobility of theadsorbed surface species and improve the kinetics of formation for theself-assembled monolayer.

Exemplary Process Embodiment 3

A moveable substrate with a levitation stabilizing structure employed ina surface modification process with pneumatic levitation.

Another method embodiment comprises a moveable substrate with levitationstabilizing structure that is placed in process apparatus 150 upon agas-emanating stationary support through which fluid will flow for thepurposes of preparing an adhesion promoting layer on the surface of themoveable substrate through exposure of the moveable substrate surface tovapors of the adhesion promoting chemical reagent hexamethyldisilizaneor HMDS. HMDS was first described in U.S. Pat. No. 3,549,368 by R. H.Collins and F. T. Devers of IBM (1970) as a photoresist adhesionpromoter for semiconductor applications. Since then HMDS vapor priminghas become a well understood and preferred technique for photoresistcoating applications. HMDS resist adhesion promotion allows for reducedchemical consumption and substrate surface modification that can bechemically stable for several weeks. In addition to aiding proper resistadhesion, HMDS also helps control surface moisture levels on thesubstrate. Surface moisture is an additional factor that can degraderesist adhesion and result in resist pattern peel off or unwantedlateral etching through the cracks under the resist. Like the surfacemodification method of hypothetic process embodiment 2, the purpose ofvapor priming is to change the surface properties of the moveablesubstrate in such a way as to change the surface energy and the chemicalreactivity. HMDS vapor prime produces specific surface chemistry thatpromote adhesion of photoresist formulations. The moveable substratewith levitation stabilizing structure is placed in processing apparatus150 so that the levitation stabilizing structure is facing or opposingthe gas-emanating stationary support and the moveable support ispneumatically levitated by a gaseous fluid. The stationary supportcontains a fluid collimating conduit in fluid communication with a gascontaining a reactive vapor phase precursor that is generated byapparatus 20. The gas containing a reactive vapor phase precursor mayoptionally be a compound fluid flow, said fluid flow being either acoaxial compound fluid flow or a collinear compound fluid flow. Thegaseous fluid composition is chosen to contain a reactive vapor phaseprecursor—HMDS—that reacts with the moveable substrate surface in such away as to uniformly expose the moveable substrate surface to themolecular vapor of the reactive precursor with the intent of forming amolecular layer or monolayer of a chemical composition similar to thereactive precursor on the surface of the moveable substrate. Pneumaticlevitation with radial flow is used as method for exposing the moveablesubstrate surface to a molecular flux of the reactive precursor. Theconditions of radial flow during pneumatic levitation are favorable forthe formation of uniform molecular layers because, as previouslydiscussed, the exposure of the moveable substrate surface (which equalsthe molecular flux to the surface multiplied by the amount of time thesurface is in contact with the molecular flux) is uniform over theentire surface area that is exposed to radial flow. In one embodiment,the substrate is a silicon wafer with a hydrated silicon oxide surfaceand the reactive vapor phase precursor is hexamethyldisilazane which isknown to be highly reactive with hydrated silicon oxide surfaces and isused for the formation of lower surface energy surfaces that are stillchemically reactive with photoresist formulations. Exposure of thehydrated silicon oxide surface of the substrate to vapor phase HMDS willresult in liberation of NH₃ gas and the formation of a triethylsiloxanemonolayer that is chemically bonded to the silicon oxide surface wherethe organic functional groups are oriented so that they face outwardsfrom the substrate surface, thereby imparting substantially different,hydrophobic properties to the silicon oxide surface while stillretaining the chemical reactivity of the trimethylsilane functionalgroup. Additionally, pneumatic levitation with optional heating of themoveable substrate and levitation stabilizing structure can be usedduring, prior or after moveable substrate processes like the HMDS vaporprime process to carry out a method of pneumatically levitated thermalannealing or thermal dehydration.

Exemplary Process Embodiment 4

A moveable substrate with a levitation stabilizing structure employed ina vapor phase dry etching process with gaseous hydrofluoric acid withpneumatic levitation.

In another method embodiment a moveable substrate with levitationstabilizing structure is placed in a chamber upon a gas-emanatingstationary support. The moveable substrate is placed in processingapparatus 150 so that the levitation stabilizing structure is facing oropposing the gas-emanating stationary support and the moveable supportis pneumatically levitated by a gaseous fluid. The stationary supportthrough which fluid will flow contains an fluid collimating conduit influid communication with a gas containing a reactive vapor phaseprecursor that is generated by apparatus 20. The gas containing areactive vapor phase precursor may optionally be a compound fluid flow,said fluid flow being either a coaxial compound fluid flow or acollinear compound fluid flow. The gaseous fluid composition is chosento contain a reactive vapor phase precursor that reacts with themoveable substrate surface in such a way as to uniformly expose themoveable substrate surface to the molecular vapor of the reactiveprecursor with the intent of removing or etching away portions of thesurface of the moveable substrate by surface reactions that producevolatile products. Pneumatic levitation with radial flow is used asmethod for exposing the moveable substrate surface to a molecular fluxof the reactive precursor. An example of a vapor phase reactiveprecursor that is used for the purpose of removing portions of asubstrate is gaseous hydrofluoric acid, HF. HF is used in vapor phaseetching of silicon substrates in the fabrication of microelectromechanical systems on silicon wafer substrates. The HF etch is anisotropic process that etches all surface exposed to the HF vapor andprovides a method of achieving a dry isotropic etch as part of thefabrication of microelectromechanical systems in silicon. The conditionsof radial flow during pneumatic levitation are favorable for theformation of surface exposure because, as previously discussed, theexposure of the moveable substrate surface (which equals the molecularflux to the surface multiplied by the amount of time the surface is incontact with the molecular flux) is uniform over the entire surface areathat is exposed to radial flow. As mentioned, in one embodiment, thesubstrate is a silicon wafer with regions of the wafer selectivelypatterns for exposure to a vapor phase etching agent and the reactivevapor phase etching agent is hydrofluoric acid vapor. An optional inertcarrier gas can be employed to minimize the amount of HF gas used.Exposure of the hydrated silicon oxide surface to vapor phase HF willresult in liberation of water and silicon tetrafluoride gas thus thesilicon oxide surface is etched away from the moveable substrate surfaceand removed in the form of volatile products. The rapid radial flow inthe volume between the moveable support surface with its levitationstabilization structure and the gas-emanating stationary support enablesrapid etch product removal and excellent cleanliness during the etchingprocess thereby ensuring that the etch process is limited only bydiffusion of the gas phase reactive species—in this case, HF—to themoveable substrate surface. The effluent from the etch process ismanaged by the use of a supplemental laminar flow of inert gas aroundthe moveable substrate and stationary support for the purpose ofremoving the gaseous process effluent from the process chamber fordisposal. It is recognized that temperature control of the process isadvantageous. Process temperature control can be achieved through, forexample, supplemental heating or cooling of process gases by such meansas, for example, heating or cooling of the reactive gas stream or,alternatively, heating the moveable substrate by inductive heating orradiative heating.

Exemplary Process Embodiment 5

A moveable substrate with a levitation stabilizing structure employed ina temperature controlled process with pneumatic levitation—an example ofwhich is a thermal annealing process with pneumatic levitation.

Another method embodiment comprises a moveable substrate with levitationstabilizing structure that is placed in process apparatus 150 upon thegas-emanating stationary support through which fluid will flow andexposing the moveable substrate to thermal energy for the purpose ofthermal annealing of the moveable substrate or carrying out thermallypromoted processes like thermal dehydration, thermal polymerization, orthermal treatment for the purpose of changing crystallite size orrelieving stress in the moveable substrate. The moveable substrate isplaced so that the levitation stabilizing structure is facing oropposing the gas-emanating stationary support and the moveable supportis pneumatically levitated by a chemically inert gaseous fluid. Thestationary support contains an fluid collimating conduit in fluidcommunication with an inert gas such as a helium, neon, argon, kypton,or xenon or nitrogen. The stationary IR transmitting gas emanatingsupport is made of, for example—vitreous silicon oxide or some otherinfrared transmitting (IR) material, and equipped with an infraredradiation source such as a high intensity T-3 quartz halogen lamp withsuitable reflectors positioned to provide a uniform radiation field onthe surface of the opposing moveable substrate when IR radiation istransmitted through the IR transmitting gas-emanating stationary supportonto the opposing surface of the moveable substrate surface. Optionally,the moveable substrate with a levitation stabilizing structure can beirradiated with, for example, a T-3 quartz halogen irradiation source,from the opposite side of the moveable substrate—that is, the side ofthe moveable substrate that does not face the gas-emanating stationarysupport. The gaseous fluid composition may optionally be chosen to havea minimal infrared adsorption at the emission wavelengths of theradiation source so as to maximize transmission of infrared energy tothe moveable substrate for the purpose of raising the temperature of themoveable substrate by infrared radiation adsorption. Alternatively, thegaseous fluid can be heated by any means familiar to those skilled inthe art of process temperature control. Such methods include the use ofresistive heaters, inductive heaters, radiative heaters, heat exchangersusing secondary heating or cooling reservoirs in conjunction with a heatexchanging assembly, and the like. The temperature of the substrate orof the gaseous fluid itself can be measured for the purposes of processcontrol by controlling the thermal energy imparted to the moveablesubstrate or the gaseous fluid itself. Temperature measurement methodsare well known and include the use of infrared thermocouples andinfrared temperature sensors, thermocouples, resistive thermaldetectors, temperature sensitive diodes, temperature controlledoscillators whose oscillation frequency changes with temperature,temperature sensitive fluorescence measurements where the decay time offluorescence varies with temperature and any other methods known tothose skilled in the art of temperature measurement. Pneumaticlevitation with radial flow is used as method for thermally isolatingthe moveable substrate and its surfaces from physical contact with anythermal sinks, thereby enabling the most effective use of temperaturecontrol and effective use of infrared radiative heating. The rapidradial flow in the volume between the moveable support surface with itslevitation stabilization structure and the gas-emanating stationarysupport enables excellent cleanliness during the heating process as wellas the capability to induce rapid cooling when heating is discontinued.The effluent fluid from the process is managed by the use of asupplemental laminar flow of inert gas around the moveable substrate andstationary support for the purpose of removing the gaseous processeffluent from the process chamber for disposal. U.S. Pat. No. 5,370,709has previously disclosed thermal annealing processes and depositionusing reactive precursors by employing pneumatic levitation with asingle orifice but the apparatus disclosed therein required the use ofphysical stops to prevent the substrate from sliding off the “suctionplate”. Therefore thermal annealing during pneumatic levitation withoutthe use of substrate motion restraining structures such as physicalstops on the stationary support plate was not contemplated in U.S. Pat.No. 5,370,709.

Exemplary Process Embodiment 6

A moveable substrate with a levitation stabilizing structure employed ina deposition process with aerosols wherein pneumatic levitation isemployed to promote even and uniform disposition of aerosol particlesupon the moveable substrate surface during pneumatic levitation.

Another method embodiment comprises a moveable substrate with levitationstabilizing structure that is placed in processing apparatus 150 upon agas-emanating stationary support through which fluid will flow andexposing the moveable substrate to an aerosol gaseous fluid optionallywith thermal energy for the purpose of deposition of the aerosolparticles on the moveable substrate with optional thermal annealing ofthe moveable substrate or carrying out thermally promoted processes likethermal dehydration, thermal polymerization, or thermal treatment forthe purpose of changing the properties of the surface of the moveablesubstrate. The moveable substrate is placed so that the levitationstabilizing structure is facing or opposing the gas-emanating stationarysupport and the moveable support is pneumatically levitated by a gaseousfluid that is generated by apparatus 20. The gas containing an aerosolmay optionally be a compound fluid flow, said fluid flow being either acoaxial compound fluid flow or a collinear compound fluid flow. Theaerosol can be a chemically reactive aerosol that undergoes chemicalreaction with the substrate surface upon contact with the substratesurface. The stationary support through which fluid will flow containsan fluid collimating conduit in fluid communication with a gas such asan inert gas like helium, neon, argon, kypton, or xenon or nitrogen andthe gas may contain aerosol particles, said aerosol particles beingeither solid, liquid, or a combination of solids suspended in a liquidmatrix. Optional temperature control methods as previously described canbe employed for temperature of the process. The aerosol can beoptionally be generated through the use of supercritical fluids such asCO₂ or through the use of any method known to those skilled in the artof gaseous aerosol formation. Examples of methods for preparing gaseousaerosols includes the use of atomizers and nebulizers, ultrasonicatomizers, electrospray devices, and the use of other devices designedto prepare small particles the remain essentially dispersed in a gasphase fluid. For example, the aerosol can be prepared by dispersion ofnanoparticulate material in a gaseous stream followed by cyclonicseparation to promote aerosol particle size uniformity prior to fluidentry to apparatus 20. The gas-emanating stationary support can be IRtransmitting and made of, for example—vitreous silicon oxide or someother infrared transmitting (IR) material, and equipped with an infraredradiation source such as a high intensity T-3 quartz halogen lamp withsuitable reflectors positioned to provide a uniform radiation field onthe surface of the opposing moveable substrate when IR radiation istransmitted through the IR transmitting gas-emanating stationary supportonto the opposing surface of the moveable substrate surface. Optionally,the moveable substrate with a levitation stabilizing structure can beirradiated with, for example, a T-3 quartz halogen irradiation source,from the opposite side of the moveable substrate—that is, the side ofthe moveable substrate that does not face the gas-emanating stationarysupport. The gaseous fluid composition can be chosen to have a minimalinfrared adsorption at the emission wavelengths of the radiation sourceso as to maximize transmission of infrared energy to the moveablesubstrate for the purpose of raising the temperature of the moveablesubstrate by infrared radiation adsorption. Alternatively, the gaseousfluid can be heated by any means familiar to those skilled in the art ofprocess temperature control. Such methods include the use of resistiveheaters, inductive heaters, radiative heaters, heat exchangers usingsecondary heating or cooling reservoirs in conjunction with a heatexchanging assembly, and the like. The temperature of the substrate orof the gaseous fluid itself can be measured for the purposes of processcontrol, the process control employed as a controlling the thermalenergy imparted to the moveable substrate or the gaseous fluid itself.Temperature measurement methods are well known and include the use ofinfrared thermocouples and infrared temperature sensors, thermocouples,resistive thermal detectors, temperature sensitive diodes, temperaturecontrolled oscillators whose oscillation frequency changes withtemperature, temperature sensitive fluorescence measurements where thedecay time of fluorescence varies with temperature and any other methodsknown to those skilled in the art of temperature measurement. Withoutwishing to be bound by theory, it is considered that an aerosol particlecan be thought of as a very large molecular assembly. Pneumaticlevitation with radial flow is used, then, as method for exposing themoveable substrate surface to a flux of particles or a flux of largemolecular assemblies. The conditions of radial flow during pneumaticlevitation are favorable for the formation of uniform particulate layerfrom an aerosol because, as previously discussed, the exposure of themoveable substrate surface (which equals the particle flux to thesurface multiplied by the amount of time the surface is in contact withthe particle flux) is uniform over the entire surface area that isexposed to radial flow. The aerosol fluid flow and subsequent aerosoljet emitted from fluid collimating conduit 14 can be compound fluidflows produced by apparatus 20 and can be collinear or coaxial and thecompound fluid flow may consist of more than two chemically distinctcomposition regions that are temporally separated thereby depositingmore than one type of aerosol on the surface of the moveable substrate.The temporal variation in the composition of the compound jet isachieved through the use of temporal—that is, time based—sequencing ofvalves of processing apparatus 150 by employing valve sequence controlunit 1555 to control the chemical composition of the fluid passingthrough apparatus 20.

The use of a repeat sequence in steps 74-78 in process 70 for exposureof a levitated substrate to a reactive fluid flow is not specific to thetype or state of matter of the reactive fluid. For example, the reactivefluid can be comprised of aerosol particles, liquid or solid or mixedliquid and solid. The temporally variable exposure of the surface of themoveable substrate to aerosols of different chemical compositions can beadvantageous in a number of processes including monolayer formationprocesses using aerosol based precursors. Thus the use of aerosoldeposition by the inventive pneumatic levitation deposition methodallows the construction of multilayer particular structures for varioustechnical applications. For example, the method disclosed in exemplaryprocess example 6 can be employed to prepare a multilayer structure ofnanoparticulate materials that allows the formation of nanoparticulatecomposite materials with surface unique properties. In one exampleembodiment, a multilayer varnish that is optically transparent can beapplied by such a method on optics to furnish anti-reflective coatingsor anti-scratch coating. In another embodiment, a multilayer varnishthat is optically transparent can be applied by such a method on anintegrated thus providing encapsulation for integrated or otherelectronic components for improved environmental robustness.

Pneumatic levitation with radial flow can be used concurrently withaerosol deposition to provide a method for thermally isolating themoveable substrate and its surfaces from physical contact with anythermal sinks, thereby enabling effective temperature control for bothheating and cooling—especially during the use of optional processingsteps involving high photon flux radiative exposures such as optionallyradiative curing with either IR or UV radiation. The use of processingsteps involving the use of radiation of all types for the purposes ofstabilizing and inducing further changes in material properties ofdeposited films during pneumatic levitation is specifically contemplatedand such radiation sources may include ionizing radiation sources suchas x-rays, gamma rays, and the like as well as lower photon energyradiation types such as ultraviolet radiation and infrared radiation.The use of microwave radiation is specifically contemplated as appliedto the pneumatic levitation of a moveable substrate with a levitationstabilizing structure. The rapid radial flow in the volume between themoveable support surface with its levitation stabilization structure andthe gas-emanating stationary support enables excellent cleanliness andlow contamination during deposition processes executed at elevatedtemperatures as well as the capability to induce rapid cooling onceheating is discontinued. The effluent fluid from the process isoptionally managed by the use of a supplemental laminar flow of inertgas from process apparatus element 1520 around the moveable substrateand stationary support for the purpose of removing the gaseous processeffluent from the region proximate to the moveable substrate and thestationary support assembly for disposal.

Exemplary Process Embodiment 7

A moveable substrate with a levitation stabilizing structure employed ina deposition process with pneumatic levitation.

Another method embodiment a moveable substrate with levitationstabilizing structure is placed in a processing apparatus 150 upon agas-emanating stationary support through which fluid will flow and thepneumatically levitated moveable substrate is exposed to thermal energyand a reactive precursor for the purpose of depositing a thin film onthe surface of the moveable substrate by thermal decomposition of thereactive precursor on the surface of the moveable substrate andadditionally carrying out thermally promoted processes like thermaldehydration, thermal polymerization, or thermal treatment for thepurpose of changing crystallite size or relieving stress in the moveablesubstrate with the deposited thin film. The process apparatus 150 isequipped with a supplemental laminar gas flow for the purpose ofmanaging the gaseous process effluent stream. The effluent fluid fromthe process is managed by the use of a supplemental laminar flow ofinert gas around the moveable substrate and stationary support for thepurpose of removing the gaseous process effluent from the processchamber for disposal. The moveable substrate is placed so that thelevitation stabilizing structure is facing in an opposing manner thegas-emanating stationary support and the moveable support ispneumatically levitated by a gaseous fluid. The stationary supportassembly 12 through which fluid will flow contains a fluid collimatingconduit 14 in fluid communication with a gas that can be chemicallyreactive with the substrate surface. The fluid can be chemicallyoxidizing, chemically reducing or chemically inert. An example of achemically oxidizing gas is oxygen gas. An example of chemicallyreducing gas is hydrogen. Examples of chemically inert gases includehelium, neon, argon, krypton, or xenon or nitrogen. The gas flowoptionally contains a reactive precursor that can be added into the gasflowing through the stationary support by coaxial or a compound fluidflow formation employing apparatus 20—the overall composition of thegaseous process fluid being adjusted by adjusting the composition of thecompound fluid by valve sequencing control unit 1555 and control valves1560 according to the desired deposition process. The flow of thegaseous fluids through the chamber and the flow of the gaseous fluidsthrough the stationary support assembly 12 in fluid communication withone or more gas sources is controlled by any means known to thoseskilled in controlling gas flow. Such means include the measurement ofgas flow and a feedback loop that includes a means for controlling thegas flow. Gas flow measurement methods include pitot tubes, rotameters,mass flow meters and the like. Gas flow control methods include the useof variable conductance valves and variable conductance orifices whosegas flow properties can be controlled by an external means. Gas flowcontrol methods also include pressure control measurements where the gaspressure across, for example, an orifice of known conductance, can beused to regulate gas flow through said orifice of known conductance. Thetemperature of the moveable substrate with levitation stabilizingstructure and optionally the temperature of the stationary supportassembly 12 through which fluid will flow can be regulated by atemperature control loop contained in moveable substrate and stationarysupport temperature control unit 1550. For example, the stationary fluidemitting support 12 can be a stationary IR transmitting gas emanatingsupport is made of, for example—vitreous silicon oxide or some otherinfrared transmitting (IR) material, and equipped with an infraredradiation source such as a high intensity T-3 quartz halogen lamp withsuitable reflectors positioned to provide a uniform radiation field onthe surface of the opposing moveable substrate when IR radiation istransmitted through the IR transmitting gas-emanating stationary supportonto the opposing surface of the moveable substrate surface. Optionally,the moveable substrate with a levitation stabilizing structure can beirradiated with, for example, a T-3 quartz halogen irradiation source,from the opposite side of the moveable substrate—that is, the side ofthe moveable substrate that does not face the gas-emanating stationarysupport thereby utilizing absorption of infrared radiation on the sideopposite the levitation stabilizing structure as a means for controllingthe temperature of the pneumatically levitated moveable substrate.Alternatively, the gaseous fluid or plurality of gaseous fluid employedin the process can be heated by any means familiar to those skilled inthe art of process temperature control optionally additionally employingfluid temperature and pressure control units 1545. Such methods includethe use of resistive heaters, inductive heaters, radiative heaters, heatexchangers using secondary heating or cooling reservoirs in conjunctionwith a heat exchanging assembly, and the like. The temperature of themoveable substrate or of the gaseous fluid itself or of both themoveable substrate and the gaseous fluid can be measured for thepurposes of process control by a feedback loop controlling the thermalenergy imparted to the moveable substrate or the gaseous fluid itselfand thereby controlling the temperature of the gaseous fluid and/or themoveable substrate. Temperature measurement methods are well known andinclude the use of infrared thermocouples and infrared temperaturesensors, thermocouples, resistive thermal detectors, temperaturesensitive diodes, temperature controlled oscillators whose oscillationfrequency changes with temperature, temperature sensitive fluorescencemeasurements where the decay time of fluorescence varies withtemperature and any other methods known to those skilled in the art oftemperature measurement. Methods for constructing feedback loops forprocess control of process variable such as temperature and gas flow arewell known to those skilled in the art of process control. Manydifferent volatile precursors can be used as reactive precursors to formcompound fluid flows with a chemically inert gas stream with theprovision that the reactive precursors will thermally decompose on thesurface of the moveable substrate with the formation of the desired thinfilm composition. Deposition reactions of this type are well known tothose skilled in the art of chemical vapor deposition. Examples ofreactive precursor molecules include volatile compounds like silaneswhich are used to prepare silicon films, organosilanes which can be usedto prepare silicon carbide films, organosilanes containing siliconnitrogen bonds which can be used to prepare silicon nitride films,alkoxysilanes containing silicon-oxygen bonds which can be used toprepare silicon oxide films, and other volatile inorganic andorganometallic compounds familiar to those skilled in the art ofchemical vapor deposition. Other examples of reactive molecules that canbe incorporated into a gaseous fluid flow employed for pneumaticlevitation are water and ozone. In some applications more than onereactive species can be desired to prepare a film of the desiredstoichiometry. The reactive precursors can be delivered into thereaction volume between the moveable substrate and the stationarysupport by a compound jet formed using fluid emanating from apparatus 20that is in fluid communication with fluid collimating conduit 14 ofstationary fluid emitting support 12 through which fluid will flow. Thereactive precursor compound fluid flow can be formed through the use ofthe apparatus 20 and the compound fluid flow can be collinear orcoaxial, and the compound fluid flow may consist of more than twochemically distinct composition regions that are temporally separatedthereby exposing the surface of the pneumatically levitating moveablesubstrate to more than one type of reactive precursor on the surface ofthe moveable substrate in a temporally sequential manner.

FIG. 14 discloses the process steps carried out in processing apparatus150 for exposure of a fluidically levitated substrate with levitationstabilizing structure to a reactive fluid flow. It is also recognizedthat the repeat sequence of step 74 through 78 can allow the surface ofthe moveable substrate with levitation stabilizing structure to beexposed to two or more chemically different fluid flows during theprocess sequence—something that is particularly important inconstructing multilayer films and coatings. The inclusion of repeatingsequences of steps 74 through 78 in process step diagram 70 is withinthe spirit and scope of the disclosed exemplary process embodiments 1through 7. The temporally variable exposure of the surface of themoveable substrate to gaseous, thermally decomposable, reactiveprecursors of different chemical compositions allows the construction ofmultilayer structures for various technical applications. It isrecognized that through the use of apparatus 20 in process apparatus 150several different gaseous, thermally decomposable, reactive precursorscan be used to form several different types of chemically distinctcompound jets from chemically distinct compound fluid flows containingthe different gaseous reactive precursors to enable the formation ofthin films of complex stoichiometry involving multiple chemicallydistinct elements. It is also recognized that a plurality of gaseous,thermally decomposable or thermally activated, reactive precursors canbe used to form compound jets from compound fluid flows to enable theformation multilayered films of a highly complex structure with uniqueoptical and electrical properties. Pneumatic levitation with radial flowis used as method for thermally isolating the moveable substrate and itssurfaces from physical contact with any thermal sinks, thereby enablingthe most effective use of substrate heating to promote thermaldecomposition of the reactive precursors on the substrate surface forthe purpose of film formation. The rapid radial flow in the volumebetween the moveable support surface with its levitation stabilizationstructure and the gas-emanating stationary support enables excellentcleanliness during the heating process as well as the capability toinduce rapid cooling once heating is discontinued. U.S. Pat. No.5,370,709 has previously disclosed deposition and thermal annealingprocesses using pneumatic levitation but the apparatus disclosed thereinrequired the use of physical stops to prevent the substrate from slidingoff the “suction plate”. Therefore deposition and annealing duringpneumatic levitation where the substrate position was stabilized by theuse of a levitation stabilizing structure and pneumatic levitation wasachieved without the use of substrate motion restraining structures suchas physical stops on the gas-emanating stationary support was notcontemplated in U.S. Pat. No. 5,370,709.

Example 17

Atomic layer deposition process embodiment at atmospheric pressure on amoveable substrate using Bernoulli levitation with a levitationstabilizing structure.

A planar 8″×8″×1″ stationary fluid emitting support through which fluidwill flow made of anodized aluminum was machined with a single 4 mm IDfluid collimating conduit in the center of the plate. An infraredheating system was facing the fluid emitting surface of the stationaryfluid emitting plate to allow heating of the levitating moveablesubstrate. The fluid collimating conduit in the stationary fluidemitting support was in fluid communication with a pressurized manifoldcontaining pressurized fluid. The valves, pressure regulator, mass flowcontrollers, power supplies, tubing, pulse generator and waveformgenerator are commercially available. The devices used in this exampleare cited below. The pressurize manifold was used to deliver argon gasas the main gaseous fluid for moveable substrate levitation and thepressurized manifold containing pressurized gas was also used to deliverchemically reactive gasses into the levitation gas flow by switchablethree way valves (Gems Sensors and Controls 3 way valve modelA3314-2m-AD-V-VO-C204). The three-way valve and associated electronicshad a minimum switching time of around 50 msec, below which the voltagepulse time was too short to initiate a change in valve position. Argongas saturated with titanium tetrachloride vapor or water vapor wasprepared by use of bubblers that were connected to three way valves asshown in FIG. 23. Referring to FIG. 23, the stationary support 12through which fluid will flow with 4 mm ID fluid collimating conduit isin fluid communication with two three way valves 96 and also in fluidcommunication with main levitation fluid regulator 1600. The mainlevitation fluid regulator controls the majority of the flow throughfluid collimating conduit 14 of stationary support 12 to establishfluidic levitation of moveable substrate 10 with a gas. Thepressurized-gas or pressurized inert gas source 1575 supplies the mainregulator 1600 as well as two mass flow controllers 1560. A three wayvalve 96 is used to direct the flow from the each mass flow controllerso that the inert gas flow exiting valve 96 is either chemically inertor saturated with a reactive chemical species by either reactiveprecursor source 1 1565 or reactive precursor source 2 1570. Againreferring to FIG. 23, when mass flow controller 1560 is operational, thereactive precursor sources 1565 and 1570 are pressurized and the threeway valve 96 serves to determine whether the inert gas flow exitingthree way valve 96 passes through the reactive precursor source or not.Reactive precursor sources 1 and 2 are room temperature bubblerscontaining deionized water and titanium tetrachloride, respectively. 99%pure titanium tetrachloride was obtained from Fluka Chemicals. Themoveable substrate with levitation stabilizing structure was comprisedof a 150 mm diameter silicon wafer with a 225 micron thick resist ringprepared from Dupont WBR2120 dry film resist. The resist ring had an IDof 128 mm and an OD of 130 mm and was prepared as described in example14. The moveable substrate was placed over the fluid collimating conduitof the stationary fluid emitting support and an argon gas flow wasinitiated using approximately 9 psig levitation pressure (about 70 slpmAr). Mass flow controllers were used to provide an initial flow of 1slpm argon through each 3 way valve that served to establish an inertgas flow through the delivery lines for the reactive gases as well aspressurize the reactive precursor sources for delivery of the chemicallyreactive fluid into the main inert gas flow. The infrared heating systemwith T3 lamps was used to bring the levitating moveable substrate waferto approximately 160+−10 degrees C. The moveable substrate withlevitation stabilizing structure showed stable pneumatic levitation withlimited oscillatory lateral motion even at the elevated processoperating temperature. After temperature stabilization, an atmosphericpressure atomic layer deposition pulse sequence was initiated using amultichannel digital signal generator (Stanford Research InstrumentsDG535 Delay/Pulse Generator) to control the sequencing of the three wayvalves. Repetitive valve sequencing was accomplished by triggering themultichannel digital signal generator with an external logic signalfurnished by a digital waveform generator (Wavetek model 29A). Thepneumatically levitated moveable substrate with levitation stabilizingstructure was exposed to 100 atomic layer deposition cycles comprised ofa 500 msec water pulse, a 500 msec inert gas purge pulse, a 150 msectitanium tetrachloride pulse, and a 500 msec inert gas purge pulse.After the atomic layer deposition cycles were complete, the infraredheating lamp was turned off and the moveable substrate was allowed tocool while pneumatically levitating. After cooling the levitation wasdiscontinued and the sample was removed for examination by variablewavelength ellipsometry. Ellipsometry showed that a 63±2 Å TiO2 film wasdeposited on the surface of the levitated substrate with a refractiveindex of 2.32 at 633 nm demonstrating that rapid atomic layer depositionprocesses can be performed at atmospheric pressure while pneumaticallylevitating a moveable substrate with a levitation stabilizing structure.The atomic layer deposition process disclosed in example 17 isapproximately 10 times faster than the low-pressure processes disclosedin the open scientific literature by Sinha et al (loc cit).

Example 17 discloses the atomic layer deposition of titanium oxide atatmospheric pressure using outward radial flow over the surface of amoveable substrate whose pneumatic levitation is stabilized using alevitation stabilizing structure. The temperature of the moveablesubstrate during the process was not optimized. The length of the timedpulses of water, argon inert gas, and titanium tetrachloride were notoptimized and the flow rate of argon carrier gas through the water andtitanium tetrachloride sources was 0.5 slpm. Reduction in the length ofthe timed pulses employed during the deposition process can be achievedby varying the gas flow rate through the reactive species sourcebubblers for water and TiCl₄, increasing the temperature of reactivespecies source bubblers for water and TiCl₄. As the overallconcentration of reactive species in a timed gas flow pulse increases,the pulse length can be decreased thereby reducing the overall cycletime required to execute a sequence of 4 consecutive gas pulses acrossthe surface of the moveable substrate. Faster cycle times are alsoenabled by valves with faster valve switching times between states sothat shorter gas pulses can be executed during the process. Example 17illustrates a method of controlling the fluid flow employed for anatmospheric pressure atomic layer deposition process with fluidiclevitation to provide different fluid for time periods of less than fivehundred milliseconds. In one embodiment of the atmospheric pressuredeposition method illustrated by example 17 the fluid flowing throughthe stationary support is controlled to sequentially provide first andsecond fluid flows of different fluids within the time period requiredfor the fluid to propagate from the fluid collimating conduit to thesubstrate edge so that at least two different fluids are present in thevolume gap between the moveable substrate and the stationary support atthe same time.

In one embodiment of the atmospheric pressure atomic layer depositionmethod illustrated by example 17 the fluid flowing from the stationarysupport impinging at a location on the substrate is controlled so thetime period between different fluid pulses is shorter than the timerequired for the fluid to propagate from the columnar collimated fluidjet impingement location on the substrate to an edge of the substrate.In a further embodiment of an atmospheric pressure atomic layerdeposition method the fluid flow impinging on the moveable substrate iscontrolled to sequentially provide first, second, and third fluid flowsof different fluids within the time period required for the fluid flowto propagate from the impingement location of the fluid on the substrateto the edge of the substrate so that at least three different fluids arepresent in the gap volume between the moveable substrate and thestationary support at the same time and wherein the first and thirdfluid include different reactive fluids and the second fluid is an inertfluid. The embodiments of an atmospheric pressure atomic layerdeposition method with fluidic levitation of a moveable substrate arepossible because of the high fluid velocity in the volume gap betweenthe moveable substrate and the stationary support combined with highspeed valve switching and provides a significant advantage in overallprocessing speed for the manufacture of single layer and multilayer thinfilms by atomic layer deposition or other deposition methods employingvolatile precursors.

In an embodiment of the invention, the use of valves that can beswitched at a millisecond time rate allows the user to switch betweengases at a very rapid rate, thus enabling not only a fast deposition butrapid formation of multilayer structures and is particularly useful forthe manufacturing of corrosion-resistant multilayer thin films of thetype disclosed in, for example U.S. Pat. No. 8,567,909. The depositioncycle rate can be as fast as 10 or 100 complete deposition cycles persecond and is therefore well suited to the preparation of complexmultilayer structures by atomic layer deposition methods ofmanufacturing. The deposition speed is ultimately limited by masstransport to the moveable substrate surface associated with gas meanfree path and gas diffusion to and from the moveable substrate surfacethrough boundary layers under radial flow conditions. The invention thusallows the development of high-speed atomic layer deposition clustertools for single wafer and single substrate processing in amanufacturing environment. Deposition tools for atomic layer depositionthat operate below atmospheric pressure often have large chamber volumesand, as a result, must include exposure and purge times that allow thelaminar flow of the gas in the chamber to sweep the reactive fluid flowin and out of the chamber—a process that often takes seconds toaccomplish even at high flow rates. Thus, rapid switching time of thepresent invention are not accessible because the turnover time of thechamber is large due to the larger chamber volume. Gas bearing typeatmospheric pressure atomic layer deposition tools have quite smalleffective chamber volumes but are limited in physical size by thecomplicated construction of the deposition tool gas bearing structurefor reactive fluid exposure (the deposition head). Gas bearing typeatmospheric pressure deposition tools have difficulty withtopographically complex surfaces and do not coat circular substrateswell. In spite of the obvious advantages of multiple exposure regions ingas bearing deposition methods like spatial atomic layer deposition, thegas bearing deposition head is limited in size because of the difficultyassociated with the mechanical construction of a large deposition headwith multiple deposition zones and the deposition cycle throughput islimited by the speed at which the gas bearing device can be translatedover the substrate. The present invention is significantly lessexpensive, easier to implement, and is not bound by the aforementionedlimitations.

The invention has been described in detail with particular reference tocertain embodiments thereof, but it will be understood that variationsand modifications can be effected within the scope of the invention.

The invention claimed is:
 1. A fluidic levitation system for levitatinga moveable substrate, comprising: a moveable substrate having alevitation stabilizing structure attached to and protruding from themoveable substrate, the levitation stabilizing structure forming aclosed geometric shape that surrounds and encloses an enclosed interiorimpingement area of the moveable substrate; a stationary support locatedproximate to the moveable substrate, the stationary support extendingbeyond the enclosed interior impingement area; and a pressurized-fluidsource that provides a fluid flow through the stationary support thatimpinges on the moveable substrate within the enclosed interiorimpingement area of the moveable substrate sufficient to levitate themoveable substrate due to a Bernoulli lift force caused by theimpingement of the fluid flow onto the moveable substrate, therebyforming a gap between the moveable substrate and the stationary supportand exposing the moveable substrate to the fluid, wherein fluid flowimpinging on the levitation stabilizing structure restricts the lateralmotion of the moveable substrate during levitation.
 2. The fluidiclevitation system of claim 1, wherein the fluid flow provided throughthe stationary support impinges proximate to a centroid of a surface ofthe moveable substrate.
 3. The fluidic levitation system of claim 1,wherein the fluid flow provided through the stationary support impingesproximate to a centroid of the enclosed interior impingement area of themoveable substrate.
 4. The fluidic levitation system of claim 1, whereinthe stationary support is located beneath the moveable substrate.
 5. Thefluidic levitation system of claim 1, wherein the stationary support islocated above the moveable substrate.
 6. The fluidic levitation systemof claim 1, the stationary support including a fluid collimating conduitthrough which the fluid flows, wherein the fluid collimating conduit hasa cross sectional area that is less than or equal to ¼ of the areaenclosed by the levitation stabilizing structure.
 7. The fluidiclevitation system of claim 1, the stationary support including a fluidcollimating conduit through which the fluid flows, wherein the fluidcollimating conduit has a cross sectional area that is less than orequal to ¼ of the area of the surface of the moveable substrate on whichlevitation stabilizing structure is located.
 8. The fluidic levitationsystem of claim 1, wherein the levitation stabilizing structure has aheight extending away from the moveable substrate that is less than ⅔ ofthe gap between the moveable substrate and the stationary support whenthe moveable substrate is levitated.
 9. The fluidic levitation system ofclaim 1, wherein the levitation stabilizing structure has a heightprotruding from the moveable substrate that is between 50 microns and 5mm.
 10. The fluidic levitation system of claim 1, wherein the levitationstabilizing structure has a constant height.
 11. The fluidic levitationsystem of claim 1, wherein the moveable substrate further includes anadditional structure attached to and protruding from the moveablesubstrate, the additional structure being located within the enclosedinterior impingement area of the levitation stabilizing structure. 12.The fluidic levitation system of claim 11, wherein the additionalstructure has a height that is less than a height of the levitationstabilizing structure.
 13. The fluidic levitation system of claim 11,wherein the additional structure is solid.
 14. The fluidic levitationsystem of claim 11, wherein the additional structure forms a closedcurve.
 15. The fluidic levitation system of claim 1, wherein thestationary support extends beyond the moveable substrate.
 16. Thefluidic levitation system of claim 1, wherein the moveable substrate issubstantially non-planar.
 17. The fluidic levitation system of claim 16,wherein the substantially non-planar moveable substrate includes aspherical section.
 18. The fluidic levitation system of claim 16,wherein the substantially non-planar moveable substrate includes astructured surface.
 19. The fluidic levitation system of claim 1,wherein the levitation stabilizing structure is attached to the movablesubstrate using an adhesive.
 20. The fluidic levitation system of claim1, wherein the levitation stabilizing structure includes a curablematerial with cross-linking agents.
 21. The fluidic levitation system ofclaim 1, wherein the levitation stabilizing structure is mechanicallyand releasably attached to the moveable substrate.
 22. The fluidiclevitation system of claim 1, wherein the levitation stabilizingstructure includes a deposition inhibiting layer.